Please review Pygments lexer and style

[Jean Abou Samra]

Hello,

Pygments is a Python syntax highlighter supporting many
languages, used by Sphinx-documented projects, users of
the 'minted' LaTeX package, Wikipedia, and various websites.
I'd like to see Pygments supporting LilyPond. Here is my
pull request (the equivalent of a merge request, on GitHub):

https://github.com/pygments/pygments/pull/1845

(Note that there is a previous attempt,
https://github.com/pygments/pygments/pull/1371. However,
it is far less precise, does not understand Scheme, and,
above all, reuses code covered by the GPL from Frescobaldi,
making it unsuitable for inclusion in the BSD-licensed
Pygments.)

Reviews and testing would be appreciated. In particular,
if you would not like to have a later unpleasant surprise
with my aesthetic choices, please give the style a look;
the eventual goal would be to make this used in our
documentation. The setup to start testing is
(assuming Python 3 installed):

git clone https://github.com/Jean-Abou-Samra/pygments.git
cd pygments
git checkout lilypond
python3 -m venv pygments-env
source pygments-env/bin/activate
pip install -r requirements.txt

Then you can highlight file.ly, outputting to file.html,
using

python -m pygments -f html -O full,style=lilypond file.ly > file.html

(If you begin a new session of testing, don't forget
to start with 'source pygments-env/bin/activate'.)

To whet your appetite, a highlighted version of the test
file included in the PR is attached.

Cheers,
Jean

example.html
Description: Text document

example.ly
Description: Text Data