Governance for this project

[k8hertweck]

As discussed in meeting on 22 April 2021:

• create a governance document for this repository
• move relevant information from contributing document to governance
• reference information about process from this issue
• clarify other necessary information so that we're modeling what we teach

[k8hertweck]

Mention from @lwjohnst86 : we need to figure out governance following publication of the book! We can revisit this in ~6 months

[lwjohnst86]

Considering you have a fair amount already, do you want me to start this and you can review/add to in a PR?

[k8hertweck]

Yes, that would be great, thanks!