feat: New rule: tag-no-obsolete

[coliff]

https://htmlhint.com/rules/tag-no-obsolete/

What it does:

Disallows the use of obsolete HTML5 tags
Detects both opening and closing tags
Case-insensitive detection (works with <CENTER>, <center>, etc.)

Obsolete tags detected:

applet, acronym, bgsound, dir, frame, frameset, noframes
isindex, keygen, listing, menuitem, nextid, noembed
plaintext, rb, rtc, strike, xmp, basefont, big
blink, center, font, marquee, multicol, nobr, spacer, tt

Files created/updated:

✅ src/core/rules/tag-no-obsolete.ts - Rule implementation
✅ src/core/rules/index.ts - Rule export
✅ src/core/types.ts - TypeScript interface
✅ test/rules/tag-no-obsolete.spec.js - Test suite
✅ website/src/content/docs/rules/tag-no-obsolete.mdx -
Documentation
✅ website/src/content/docs/rules/index.mdx - Rules index

Test results:

✅ All 4 tests pass
✅ Documentation test passes
✅ All existing tests still pass
✅ Manual testing confirms the rule works correctly

The rule is now fully integrated into HTMLHint and ready to use! Users can enable it by adding tag-no-obsolete: true to their HTMLHint configuration.

[gemini-code-assist]

Code Review

This pull request introduces a new linting rule tag-no-obsolete to disallow the use of obsolete HTML5 tags. The implementation is clear, accompanied by comprehensive tests and documentation. I have a suggestion for a potential performance optimization in the rule implementation by using a Set for the list of obsolete tags, and another regarding the visibility of the new rule in the documentation index.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (95e6a13) to head (c2e4863).
Report is 81 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #1660      +/-   ##
===========================================
+ Coverage   96.99%   100.00%   +3.00%     
===========================================
  Files           2         1       -1     
  Lines        1628         1    -1627     
  Branches      335         0     -335     
===========================================
- Hits         1579         1    -1578     
+ Misses         49         0      -49     

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