Support for LilyPond

[aiomaster]

What problem does this feature solve?

Highlighting of *.ly files used by the music program LilyPond

What feature do you propose?

Just use the lexer and styles from pygments:

https://github.com/pygments/pygments/blob/master/pygments/lexers/lilypond.py
https://github.com/pygments/pygments/blob/master/pygments/styles/lilypond.py

I would have made a Pull request, but I was not able to use the _tools/style.py conversion tool, cause there are no docs and I couldn't figure out the right arguments for it.