Prettified codebase

[AnimeAllstar]

• setup prettier config file for the repo
• ran prettier on the entire repo
• updated docs
• added GitHub Action that creates a commit on PRs to master if the code isn't prettified. (We could do this in the same commit, but I thought it'd be better to have a different commit). This happens before the merge when all the deploy preview tests are running. If you add a second commit with bad formatting to a live PR, it'll make another commit to the PR formatting your code.

You will have to run yarn install when you pull changes to run prettier locally.

Let me know what y'all think. We can definitely update the prettier config if there are any changes that should be made.

closes #324

[kewbish]

We have a bit of a chicken and egg situation here: I can't run the GitHub action on this repo if it hasn't been merged here, but I saw on your personal fork that you've tested it and it works, so I'm comfortable with approving.

This should be revertible if things go wrong (and if they go wrong, Netlify won't build the latest version and will continue to serve the old version) so we should be safe. Netlify successfully built this PR, so there shouldn't be any issues.

I left a couple nits below, feel free to address or leave them.

Thanks so much for taking this on!