feat(divider): add divider component

[manika-signoz]

Summary

Introduces a new Divider component for visually separating content, with horizontal/vertical orientations, dashed lines, optional centered labels, and Storybook/docs wiring.

Changes

Component (@signozhq/ui)

• New Divider component (divider.tsx, divider.module.css, index.ts).
• Props:
  • type — 'horizontal' | 'vertical' (default: 'horizontal')
  • dashed — Dashed line style
  • plain — Plain text style for label (when children provided)
  • testId, className, standard div passthrough
• Accessibility: When no children, renders role="separator" with aria-orientation matching type.
• data-slot="divider" plus data-type, data-dashed, data-plain, data-with-text for styling/testing.

Package exports

• ./divider subpath in package.json
• Barrel export in src/index.ts
• Vite lib entry in vite.config.ts
• Divider import added to root README.md and intro.mdx

Docs & Storybook

• New divider.mdx and divider.stories.tsx under Components/Divider
• Stories: Playground, Horizontal, Vertical, Dashed, With text, Plain text

Tests

• Forward-ref test for Divider.