Clean up source variable docs

[jmbannon]

Source variables are information from the media downloaded from ytdlp that can be used to set file names or metadata. They are documented here:
https://ytdl-sub.readthedocs.io/en/latest/config.html#source-variables

If you notice, a few variables' formatting looks weird. Like this one:
https://ytdl-sub.readthedocs.io/en/latest/config.html#ytdl_sub.entries.variables.youtube_variables.YoutubeVideoVariables.artist

There are random asterisks, and it seems like the NOTE changes formatting in some way.

The documentation for these should get cleaned up. They are generated from the docstrings in here:
https://github.com/jmbannon/ytdl-sub/tree/master/src/ytdl_sub/entries/variables

The docs are created using reStructuredText (https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html) and the autodocs extension (https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html)

To build the docs locally, run make docs

[glunkad]

Hey @jmbannon , I'm interested in contributing to this issue, so before I start working on it, would you mind sparing your time explaining what the issue is about and pointing me to some resources to get started .

[jmbannon]

Hi @9gl , thanks for your interest! I added a better description and some code links. Let me know if you have any questions :)