Highlight.js language support

### What is wrong?

Currently even https://fe-lang.org/ uses `python` language for highlight.js library syntax highlighting. It may be handy for educational and other Fe-related resources to use dedicated syntax highlighter for Fe.

### How can it be fixed

Contribute Fe language support to [hightlight.js](https://github.com/highlightjs/highlight.js). Good reference is a [Python implementation](https://github.com/highlightjs/highlight.js/blob/main/src/languages/python.js).

Start with highlight.js's src/languages/python.js, which the issue names as a reference, and review how Fe syntax is represented on fe-lang.org. Contribute dedicated Fe language support to highlight.js and verify that Fe-related resources can use it instead of Python highlighting.

Written by the indexing model from the issue text.