Add CONTRIBUTING.md

[garricn]

As I was going through all the feedback on Twitter and Github, I was inspired to create the work in progress document which could serve as a guide for creating new episodes of the podcast. If I’m someone that’s interested in producing an episode, I should be able to go to a document like this and know what my next steps are. The flow I’m thinking is this:

1. “I want to produce an episode!”
2. Go to Repo > README > General Contributing guide > Episode Contributing Guide > Create Episode Proposal via template script > Open Episode Proposal pull request > Fill all roles
3. Once enough support is behind the PR and some/most/all(?) roles are filled, it gets merged which means its green lit.
4. After the episode is recorded, a PR is created with the master episode file and show notes (this brings up an interesting question of an episode being available prior to publishing)
5. Core team reviews episode and merges PR
6. Publish > Marketing, etc...

[lattner]

This LGTM! ready to merge?

[marcusrossel]

@ercillagorka is there something holding up this merge?

[jessesquires]

If you name this: .github/CONTRIBUTING.md, then GitHub recognizes this and will display an alert to new contributors to read it 😄