Validate the release process docs

[nimbinatus]

Document the project's release process.

Should be a link to the right doc.

[mohan-shash]

I've created an initial draft of RELEASES.md to document bootc's release process for CNCF incubation. The draft is available on my fork in the add-releases-documentation branch:

Preview: https://github.com/mohan-shash/bootc/blob/add-releases-documentation/RELEASES.md

What's Documented
The draft provides documentation based on the existing automated release workflows:

• Versioning - Semantic versioning standards, adhered to strictly since v1.2.0
• Release Cadence - Weekly releases since v1.16.0, automated via scheduled GitHub Actions every Monday at 8:00 AM UTC
• Automated Process - Step-by-step explanation of how the release workflows create PRs, tag releases, and upload assets
• Release Assets - Vendor archive and source tarball for each release
• Stability Guarantees - CLI and API compatibility commitments for upgrades
• GPG Signing - How to verify release tags for authenticity

Critical Questions
Before finalizing the PR, I need input on three policy decisions that aren't currently documented anywhere:

1. Support Policy
   How long is each bootc release supported? Given the weekly cadence, I'm assuming we only support the latest release and encourage users to upgrade weekly. I do not believe we support an overlap support period, right?

2. Backporting Policy
   What changes qualify for backports to older releases? With weekly releases, it seems reasonable to say all fixes go into the next weekly release rather than backporting. Are we good with that?

3. Release Branches
   Are release branches (like release/1.16) created for long-term maintenance? The current workflows show all releases tagged directly from main, which suggests no separate branches. I want to confirm this is the intended strategy before documenting it.

Next Steps
I'd like to discuss these three questions at the community Friday meeting to get maintainer consensus, then finalize the PR accordingly.

Thoughts?