Add a release checklist

[calebschoepp]

It would be nice to have a standardized release checklist that is available to all SpinKube contributors.

[macolso]

When you say release checklist, are you envisioning:

• guidance for contributors in a long form document like contributor.md
  or
• issue template that has checkboxes for the contributor to review (similar to how we do doc contributions today)
  or
• guidance for how releases work (cadence, upcoming schedule, how to find release notes, how to find maintainers) in long form document like release.md

IMO I think there's a need for all 3, but trying to determine what this issue is tracking specifically

[calebschoepp]

I was envisioning option 3. Both option 1 and 2 would be valuable! Not sure if option 1 should be in governance or per repo though.