fix: use selector for JupyterLab dark mode

[agoose77]

Fixes #67 and fixes #84

[github-actions]

👈 Launch a Binder on branch executablebooks/jupyterlab-myst/agoose77/fix-dark-mode

[agoose77]

We can do more here; JupyterLab defined variables that themes can override. It's a decision as to whether we respect that or not. @rowanc1 the variables that JupyterLab uses are defined here. How confident are you that we can consume these here?

[rowanc1]

We can override everything in that tailwind config with variables, I have a local branch starting to play with getting styles inline.

For this PR, I think we can keep it to your change, and get better at styles in a next pr!

[mcauthorn]

Thanks all, after following @agoose77 over here from imarkdown (specifically, your {eval} syntax which is huge feature to our use case), I just ran into this with a custom theme that we're designing for Jupyterlab. A couple of questions:

1. In my theme config, which variables are read?
2. Is there a dev branch you could point me to so I could help test?

Thanks again for the activity here, it's looking really promising.

[mcauthorn]

Found it (it was my config) looking good!