feat(footnotes): Use footnotes from tree-sitter grammar

[kristijanhusak]

Summary

Highlight and parse footnotes using tree-sitter grammar. Grammar version was updated.

Changes

• Remove custom markup highlighting for footnote references
• Use tree-sitter to find footnote reference for jumps

Checklist

I confirm that I have:

• Followed the
  Conventional Commits
  specification (e.g., feat: add new feature, fix: correct bug,
  docs: update documentation).
• My PR title also follows the conventional commits specification.
• Updated relevant documentation, if necessary.
• Thoroughly tested my changes.
• Added tests (if applicable) and verified existing tests pass with
  make test.
• Checked for breaking changes and documented them, if any.