Add DANDI governance document

[kabilar]

• The governance document is based on the GPT-5 prompt below, and then I manually curated the document.
  • Please create a governance document for the DANDI Archive project. This document should apply to all sites (https://dandiarchive.org/, https://about.dandiarchive.org/, https://hub.dandiarchive.org/), organizations (https://github.com/dandi/, https://github.com/dandisets, https://github.com/dandizarrs) and all their repositories. The source code for the DANDI Archive is available here: https://github.com/dandi/. Format this document in markdown. Here are some example governance documents from other projects: https://bids.neuroimaging.io/collaboration/governance.html?h=governance, https://github.com/nebari-dev/governance, https://github.com/cncf/project-template/blob/main/GOVERNANCE-subprojects.md. And discuss who will review and merge pull requests.
• Once approved, update the following in the document:
  • Effective Date
  • Status

[asmacdo]

Given that it takes 30 days minimum to properly amend this doc, IMO we should move pull request requirements, draft-pr policy and possibly release process into the developers guide.

[kabilar]

@asmacdo That's fair but I kept this here because we have had discussions on who should merge, when merges should happen, etc. so I think that all aspects of pull requests should be discussed here.

[kabilar]

Hi @satra @waxlamp @jjnesbitt @mvandenburgh @candleindark @bendichter @djarecka, could you please take a look at this doc when you get a chance. Thanks.