Document Tekton results release strategy in a `release.md` file

[afrittoli]

Feature request

The results project should document its release strategy, similar to what is done by the other Tekton projects:

Pipeline Release Cadence and Process Triggers Release Cadence and Process Chains Release Cadence and Process Dashboard Release Cadence and Process Operator Release Cadence and Process CLI Release Cadence and Process

See the requirements on the community repo too.