Implement intuitive doc release process synced with app release

[mok0230]

Currently, we release on every push to the main branch: https://github.com/OpenZeppelin/docs.openzeppelin.com/blob/ded24596d5b6ac3ae618e96d518906a177dc9f95/playbook.yml#L62

Since many documentation PRs pertain to new features/changes in the main Defender app or defender-client packages, this produces somewhat of a clunky process where we need to merge multiple docs PRs only after the app is released and can result in accidental releases (or non-releases).

Many of the other docs.openzeppelin.com feeder repos release based on a different branch than main such a v-* (pushed when a new version is released). We should do something similar in Defender. Ideally we would add minimal requirements to the existing release process.