docs: move gh wiki to mdBooks

[matt1432]

To make this I setup a GitHub action that compiles every markdown file in docs/src to a mdBooks instance hosted on this repo's GitHub Page.

All the markdown files should be almost identical to the ones in the current GitHub wiki since I cloned the ags.wiki repo. However, I did some changes to the landing page and had all the links to the wiki changed to relative paths. We might need to triple check if all of those work.

If you merge this you'll need to set this up: https://github.com/peaceiris/actions-gh-pages#%EF%B8%8F-first-deployment-with-github_token
That link wasn't too clear for me but basically, because the action makes a separate branch for the mdBooks, the Page needs to use that branch. So you just need to change the settings after it deploys once like so: