[TRACKING] Define Project Versioning, Compatibility, and Release Playbook

As node-readiness-controller matures (currently v0.3.0), we need a formalised structure for versioning and support to provide stability for our users and a clear roadmap for contributors. This issue tracks the creation and documentation of our versioning strategy.

We need to do things like:

- [ ] Draft Versioning Policy: Define Semantic Versioning (SemVer) usage.
- [ ] Establish Support Lifecycle: Define how many minor versions we support (e.g., N-2).
- [ ] Create Compatibility Matrix: Document the mapping between Controller versions and Kubernetes versions.
- [ ] Write Versioning Playbook: Standardise the release process (tagging, CI, changelogs).
- [ ] Publish Documentation: Add /docs/VERSIONING.md and update README.md.

Relates to #151

[TBD - this must be discussed with maintainers first]

Start by discussing the proposed versioning and support structure with maintainers, including SemVer, the support lifecycle, and the Kubernetes compatibility matrix. Then define the release steps for tagging, CI, and changelogs, add docs/VERSIONING.md, and update README.md; completion means all listed policy and documentation areas are agreed and published.

Written by the indexing model from the issue text.