Bump browserslist to 4.28.9 and doiuse to 6.0.6

[jsnmrs]

Supersedes #216, which fails CI.

The problem

The browserslist bump in #216 pulls caniuse-lite from 1.0.30001559 to 1.0.30001810, and npm run stylelint then crashes:

TypeError: Cannot read properties of undefined (reading 'B')
    at Object.unpackFeature (node_modules/caniuse-lite/dist/unpacker/feature.js:60:29)
    at BrowserSelection.compileBrowserSupport (node_modules/doiuse/exports/index.cjs:2578:46)

The lockfile pins doiuse@6.0.2 (a transitive dependency of stylelint-no-unsupported-browser-features). That version iterates its own feature list and hands each slug to caniuse's unpacker without checking whether caniuse-lite still carries it, so a removed slug arrives as undefined. doiuse@6.0.6 guards against it:

const packedFeature = caniuse__namespace.features[feature];
if (!packedFeature) continue; // Ignore removed features

stylelint-no-unsupported-browser-features@7.0.0 already declares doiuse: ^6.0.1, so 6.0.6 was in range all along — only the lockfile held it back, and CI's npm install honors the lockfile.

The change

npm update browserslist doiuse, which resolves to browserslist 4.28.9, caniuse-lite 1.0.30001810, and doiuse 6.0.6. All three are transitive, so package.json is unchanged and the lockfile stays at lockfileVersion 2.

Verification

Reproduced both directions in an isolated sandbox using this repo's .stylelintrc, .browserslistrc, and _sass:

doiuse	caniuse-lite	stylelint exit
6.0.2	1.0.30001810	1 — the TypeError above
6.0.6	1.0.30001810	0 — clean, no new browser-feature warnings

On this branch:

• npm run stylelint — exit 0, and --fix leaves _sass/ untouched
• npm run test-content — exit 0
• npx tape tests/*.test.js — 200/200 pass

bundle exec jekyll build was not run locally (gems not installed); it already passes in CI and is unaffected by a lockfile change.

Follow-up

Not addressed here: stylelint 15 is end-of-life and about 50 rules in .stylelintrc are deprecated. Stylelint 16 removes them, and stylelint-no-unsupported-browser-features@8.x requires stylelint 16 or newer. Worth its own issue.