Organize add more dark mode and stuff

[bradp]

#5 had broken some things - this is my 2nd attempt at it.

But of course I went down a bit of a rabbit hole, so this also organizes the styles a bit more, adds linting, adds some more styles, etc etc.

TODO:

• @bradp needs to get better at doing separate PRs

[rangelojc]

I will have to personally test this one on my local environment before merging to main.

[bradp]

Before we merge this, @bradp should also open a PR on MHCT to match the new file structure