feat: Autofix tag-self-close rule

[coliff]

This pull request introduces a new autofix feature for the tag-self-close rule in the htmlhint-server and refactors existing code to simplify and improve maintainability. It also includes updates to the documentation and test cases to reflect the new functionality.

New Feature: tag-self-close Autofix

• Added createTagSelfCloseFix function to automatically convert non-self-closing void HTML elements (e.g., <img>) into self-closing tags (e.g., <img />) to comply with standards. (htmlhint-server/src/server.ts, htmlhint-server/src/server.tsR1342-R1468)
• Integrated the new autofix into the createAutoFixes function, enabling it to handle diagnostics for the tag-self-close rule. (htmlhint-server/src/server.ts, htmlhint-server/src/server.tsR1551-R1554)
• Updated the diagnostic handling logic in connection.onRequest to support the tag-self-close rule, including extracting raw tag data and ensuring proper range normalization. (htmlhint-server/src/server.ts, [1] [2] [3] [4]

Code Refactoring

• Simplified position calculations in multiple autofix functions (createAttrValueDoubleQuotesFix, createTagnameLowercaseFix, createAttrLowercaseFix, and createSpecCharEscapeFix) by replacing complex logic with a more direct approach using lineIndex. (htmlhint-server/src/server.ts, [1] [2] [3] [4]

Documentation Updates

• Added the tag-self-close rule to the list of supported autofix rules in the README.md file. (htmlhint/README.md, htmlhint/README.mdR41)
• Updated the CHANGELOG.md to document the addition of the tag-self-close autofix feature. (htmlhint/CHANGELOG.md, htmlhint/CHANGELOG.mdR8)

Test Enhancements

• Enabled the tag-self-close rule in the .htmlhintrc configuration file for testing. (test/autofix/.htmlhintrc, test/autofix/.htmlhintrcL18-R18)
• Added new test cases in tag-self-close-test.html to validate the autofix functionality for various scenarios. (test/autofix/tag-self-close-test.html, test/autofix/tag-self-close-test.htmlR1-R24)
• Included additional tag-self-close test cases in the existing test-autofixes.html file. (test/autofix/test-autofixes.html, test/autofix/test-autofixes.htmlR33-R40)

[gemini-code-assist]

Code Review

This pull request introduces an autofix feature for the tag-self-close rule and refactors existing code for better maintainability. The changes are well-implemented, with good test coverage and documentation updates.

[gemini-code-assist]

These test cases effectively validate that the autofix correctly converts non-self-closing void HTML elements into self-closing tags.