feat: add GitHub alert banner component

[mikepenz]

Renders GitHub alerts — NOTE, TIP, IMPORTANT, WARNING, CAUTION — as an accent bar with a tinted icon and title, followed by the alert's block content.

The GFM parser has emitted GFMElementTypes.ALERT nodes since markdown 0.7.5, but they fell through to the else branch of MarkdownElementInternal, so the [!NOTE] title was swallowed and the body rendered as bare children.

Changes

Follows the existing component architecture:

• MarkdownAlertType — the five markers, resolved case-insensitively from the ALERT_TITLE token.
• MarkdownAlert — mirrors MarkdownBlockQuote's bar drawing and child dispatch.
• MarkdownComponents.alert + ALERT -> dispatch, so it is overridable like every other element.
• MarkdownAlertColors / MarkdownAlertDimens / MarkdownAlertPadding — grouped configuration models, each with the usual interface + private Default* + factory shape.
• MarkdownTypography.alertTitle styles the title, MarkdownA11yLabels.alert labels the container.
• Icons are ImageVectors built via addPathNodes, so the core module keeps its compileOnly runtime/ui/foundation dependency set, and are swappable through LocalMarkdownAlertIcons.

Markdown(
    markdown,
    colors = markdownColor(alert = markdownAlertColors(note = Color.Blue)),
    dimens = markdownDimens(alert = markdownAlertDimens(barThickness = 2.dp)),
    padding = markdownPadding(alert = markdownAlertPadding(iconSpacing = 12.dp)),
)

Theming

Material's color schemes carry no slot with the semantics these alerts rely on — a green "tip", an amber "warning" — so MarkdownAlertColorDefaults ships GitHub's light and dark palettes rather than deriving them from the theme. m2 selects between them via MaterialTheme.colors.isLight; m3 has no such flag, so it derives darkness from colorScheme.background.luminance(). Every color stays overridable.

One subtlety worth reviewing

The > marker the parser leaves in the tree is a MarkdownTokenTypes.BLOCK_QUOTE, while a nested blockquote inside an alert is a MarkdownElementTypes.BLOCK_QUOTE. Same name, different type. My first pass skipped the element type, which silently dropped nested quotes. MarkdownAlert now skips only the marker token, and AlertAstShapeTest.nestedBlockQuoteIsAnElementNotAMarkerToken pins the distinction.

Breaking change

MarkdownColors, MarkdownDimens, MarkdownPadding, MarkdownTypography and MarkdownComponents each gained one member. Direct implementers of these interfaces must add the new override. Consumers of the markdownColor() / markdownDimens() / markdownPadding() / markdownTypography() / markdownComponents() factories are unaffected — the new parameters are defaulted. .api files regenerated via apiDump; the diff is signature-arity changes only, no member removals.

Testing

• AlertAstShapeTest (7 tests) pins the AST shape the component depends on.
• 44 Paparazzi snapshots across m2/m3 in light and dark: each alert type, lowercase markers, multi-paragraph bodies, headings/lists/links inside alerts, nested quotes, and an unrecognised marker degrading to a plain blockquote. No pre-existing snapshot changed.
• ./gradlew apiCheck :multiplatform-markdown-renderer:jvmTest :sample:android:verifyPaparazziDebug passes.
• Alerts added to sample.md, so all sample apps exercise them.

Not included

CHANGELOG.md is a one-line pointer to the GitHub releases page and has been untouched since the initial commit, so I left it alone — these notes are meant for the release entry instead.

[Copilot]

Pull request overview

Adds first-class rendering for GitHub-flavoured “alerts” (> [!NOTE], > [!WARNING], etc.) by introducing a dedicated MarkdownAlert element, theming/config models (colors/dimens/padding/typography), and component dispatch so alerts are overridable like other markdown elements. This closes the gap where GFMElementTypes.ALERT nodes were previously falling through and losing the alert title.

Changes:

• Introduces alert domain + rendering: MarkdownAlertType, MarkdownAlert, alert icons/colors/dimens/padding, and LocalMarkdownAlertIcons.
• Wires alert dispatch through MarkdownComponents.alert and MarkdownElementInternal (ALERT -> ...), plus a helper to resolve the alert type from the AST.
• Adds comprehensive tests/snapshots + documentation updates, and bumps the org.jetbrains:markdown version to 0.7.6 with regenerated API dumps.

Reviewed changes

Copilot reviewed 31 out of 75 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
sample/shared/src/commonMain/composeResources/files/sample.md	Adds alert examples to the sample markdown content.
sample/android/src/main/kotlin/com/mikepenz/markdown/ui/m3/AlertsTests.kt	Adds m3 Paparazzi preview coverage for alert variants and edge cases.
sample/android/src/main/kotlin/com/mikepenz/markdown/ui/m2/AlertsTests.kt	Adds m2 Paparazzi preview coverage for alert variants and edge cases.
README.md	Documents alert support, theming knobs, and icon overriding.
multiplatform-markdown-renderer/src/commonTest/kotlin/com/mikepenz/markdown/parser/AlertAstShapeTest.kt	Pins the AST shape emitted for alerts, including nested blockquote handling.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/utils/Extensions.kt	Adds ASTNode.findAlertType(...) helper to resolve an alert type from ALERT_TITLE.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownTypography.kt	Extends typography with alertTitle styling.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownPadding.kt	Extends padding model with alert: MarkdownAlertPadding.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownDimens.kt	Extends dimens model with alert: MarkdownAlertDimens.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownColors.kt	Extends colors model with alert: MarkdownAlertColors.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownAlertType.kt	Adds enum for the 5 GitHub alert markers with parsing helper.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownAlertPadding.kt	Adds alert padding model + factory.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownAlertIcons.kt	Adds alert icon model, defaults, and icon factories (no material-icons dependency).
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownAlertDimens.kt	Adds alert dimens model + factory.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownAlertColors.kt	Adds alert color model + GitHub light/dark defaults + factory.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/model/MarkdownA11yLabels.kt	Adds a11y label generator for alert containers.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/compose/MarkdownExtension.kt	Adds ALERT -> components.alert(...) dispatch.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/compose/elements/MarkdownAlert.kt	Implements the new alert rendering element (bar + icon/title + block content).
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/compose/ComposeLocal.kt	Adds LocalMarkdownAlertIcons composition local.
multiplatform-markdown-renderer/src/commonMain/kotlin/com/mikepenz/markdown/compose/components/MarkdownComponents.kt	Adds alert component slot + default implementation using MarkdownAlert.
multiplatform-markdown-renderer/api/multiplatform-markdown-renderer.klib.api	Updates public API dump for new models/functions and signature changes.
multiplatform-markdown-renderer/api/jvm/multiplatform-markdown-renderer.api	Updates JVM API dump for new alert APIs and signature changes.
multiplatform-markdown-renderer-m3/src/commonMain/kotlin/com/mikepenz/markdown/m3/MarkdownTypography.kt	Adds alertTitle default styling for m3.
multiplatform-markdown-renderer-m3/src/commonMain/kotlin/com/mikepenz/markdown/m3/MarkdownColors.kt	Adds alert colors to m3, deriving dark/light from background luminance.
multiplatform-markdown-renderer-m3/api/multiplatform-markdown-renderer-m3.klib.api	Updates m3 klib API dump for function signature changes.
multiplatform-markdown-renderer-m3/api/jvm/multiplatform-markdown-renderer-m3.api	Updates m3 JVM API dump for function signature changes.
multiplatform-markdown-renderer-m2/src/commonMain/kotlin/com/mikepenz/markdown/m2/MarkdownTypography.kt	Adds alertTitle default styling for m2.
multiplatform-markdown-renderer-m2/src/commonMain/kotlin/com/mikepenz/markdown/m2/MarkdownColors.kt	Adds alert colors to m2, selecting default palette via MaterialTheme.colors.isLight.
multiplatform-markdown-renderer-m2/api/multiplatform-markdown-renderer-m2.klib.api	Updates m2 klib API dump for function signature changes.
multiplatform-markdown-renderer-m2/api/jvm/multiplatform-markdown-renderer-m2.api	Updates m2 JVM API dump for function signature changes.
gradle/libs.versions.toml	Bumps org.jetbrains:markdown to 0.7.6.

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