Add initial MAINTAINERS document

[evankanderson]

Summary

Define a maintainership process for external contributors for Minder, including initial maintainer list (currently all Stackers).

Change Type

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)
• Governance change

Testing

N/A

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[ethomson]

One formatting issue, and one minor nit on verbiage, but I actually wonder if this is a broader question about whether we expect this document to be rather evergreen or something that we revisit regularly? My experience is that these sorts of things often don't get updated as frequently, so something like:

Note: many project documents are currently in the Stacklok Google Drive instance. We are working to open the relevant documents for community review and feedback

Has a tendency to bitrot. I typically set the expectations that we should hold ourselves to in a document like this and then point out where we fail to do that in more dynamic / less static areas (issues, etc). But this is just my $0.02 from failing to update these sorts of docs as time changes.

[ethomson]

This para reads a little clunky to me; the automation is intentional isn't it? It doesn't feel like something we need to explain away. Maybe "because it's managed by automation" or something?

[evankanderson]

The automation is intentional, the fact that the automation is only available to Stackers because it's tied in with our general administration of https://github.com/stacklok/*, and we don't intend to open-source everything underneath that directory.

[evankanderson]

I expect us to revisit this document when we and a foundation perform due diligence on the donation of Minder to said foundation.

[coveralls]

coverage: 53.245% (+0.004%) from 53.241%
when pulling 4845647 on evankanderson:open-for-review
into 44d1523 on stacklok:main.