Syntax Highlighting Nushell (.nu) files

Proposal

It would be nice to have Nushell (.nu) files syntax highlighted.

Links

• Linguist grammar
• VSCode grammar
• Treesitter grammar

Implementation plan

1. Add lexer to Rouge.
   • Uses regex to tokenize the input.
2. Add lexer to Highlight.js
   • Uses regex to tokenize the input.
3. Add lexer to Monaco
   • Uses regex to tokenize the input.
4. Bump version of rouge. The version is defined in Gemfile.lock.
5. Bump version of highlight.js. The version is defined in yarn.lock.
6. Bump version of monaco. The version is defined in yarn.lock.

Verification

Verify that syntax highlighting works correctly in:

• repository view and diffs
• snippets
• markdown rendering