feat: Add attr-whitespace autofix

[coliff]

This pull request introduces a new auto-fix for the attr-whitespace rule in the vscode-htmlhint extension. The changes include implementing the fix logic, integrating it into the existing auto-fix framework, and updating documentation and versioning to reflect the new feature.

Implementation of the attr-whitespace auto-fix:

• Added a new createAttrWhitespaceFix function to handle attribute values with leading or trailing whitespace. This function identifies and trims whitespace in attribute values while ensuring the fix is applied only near the diagnostic position. [1] [2] [3]

• Updated the createAutoFixes function to include the new attr-whitespace rule, ensuring the auto-fix is triggered when this rule is violated.

Documentation and configuration updates:

• Added the attr-whitespace rule to the README.md file and enabled it in the .htmlhintrc configuration file. [1] [2]

• Updated the CHANGELOG.md file to document the addition of the attr-whitespace auto-fix in version 1.10.3.

Version bump:

• Incremented the extension version from 1.10.2 to 1.10.3 in package.json and package-lock.json to reflect the new feature release. [1] [2]