Docs Tutorial

[coffee-cup]

Tutorial that creates this https://github.com/prodo-ai/github-prs.

There are probably lotst fo speling mistaes an' grammer mistakes. Happy to pair with someone to go over any larger changes about content. I tried to strike a balance between no assumed knowledge and conciseness, but that is difficult to do.

[andrejak]

Also I think the best way to test the usefulness of the tutorial is to have someone external go through it, so getting this merged soon & editing after seems sensible.