chore: Add subproject owners to a central place

[FeynmanZhou]

Fix #23 also one item of https://github.com/oras-project/community/issues/28].

If this PR is approved and merged, we will sync it to the CNCF maintainer list.

[SteveLasker]

Approving to get CNCF unblocked.
That said, as noted in some of the other ORAS and Notary PRs, the relationship between CODEOWNERS, MAINTAINERS, GitHub Teams, Org and now this SUBPROJECT_OWNERS file is quite confusing.
I believe CNCF is looking for a consolidated list to point to, as noted above. This does serve the purpose, so LGTM. I just wonder how these files will stay maintained, over time.

[shizhMSFT]

LGTM

[FeynmanZhou]

Approving to get CNCF unblocked. That said, as noted in some of the other ORAS and Notary PRs, the relationship between CODEOWNERS, MAINTAINERS, GitHub Teams, Org and now this SUBPROJECT_OWNERS file is quite confusing. I believe CNCF is looking for a consolidated list to point to, as noted above. This does serve the purpose, so LGTM. I just wonder how these files will stay maintained, over time.

@SteveLasker Thanks for the heads up. You are correct. CNCF just requires a consolidated maintainer list as a reference. It requires additional efforts to maintain it indeed.

MAINTAINERS is a new role we are defining, it has the maintain permission in the repo, who will help to review PRs and manage PRs & issues. The existing OWNERS are the repo admin.

[sajayantony]

I think we should discuss this a bit more. Having 3 owner related files makes it really hard to understanding. Maybe add comments to each or collapse them and create an ORG repo for CNCF related operations.

[SteveLasker]

I think we should discuss this a bit more. Having 3 owner related files makes it really hard to understanding. Maybe add comments to each or collapse them and create an ORG repo for CNCF related operations.

Can we place the relationship of the multiple files in the governance docs?
Then, the files could have a comment, pointing to the governance docs as reference.
I'm also trying to re-use these in other projects that are also trying to solve the same problem of org and sub-project ownership.
I think this is another place to represent a great source of copy/paste for bootstrapping a new project.

[SteveLasker]

Based on our weekly meeting, I've added #36 to supersede this PR.

[SteveLasker]

@FeynmanZhou, can we close this, and review/merge #36?