Adding a tuple setup guide

[samspills]

This PR

• adds an other resources section in the main readme that calls out tuple
• adds a resources directory, and a tuple.md in that directory
  • putting it in the main directory felt a bit messy, it's definitely a different class of document than the charter
• tuple.md with instructions for getting set up
  • how to join the team for maintainers
  • quick instructions for new contributors/guests

It's "ready for review" in that I'd love to get other peoples thoughts on clarity, but also this is just my first draft. I've tried to fix my tenses but I'll definitely be giving it a second pass tomorrow.

[samspills]

Updates

• found a few other places where I wanted to fix up phrasing so I did that
• committed Justin + Andrew's suggestions (then squashed into a single commit with multiple authors)