Added 'core STAC team' from active STAC committers.
Overthrew our dictatorship, replaced with a democratic Project Steering Committee
Various minor updates to the process doc.
I'm considering no changelog needed, since it's not part of the spec / doesn't affect an implementor. But happy to put one in if desired.
PR Checklist:
[x] This PR is made against the dev branch (all proposed changes except releases should be against dev, not master).
Related Issue(s): #1019
Proposed Changes:
PR Checklist: