[Feat] Describe required updates for new version for winGRASS

[wenzeslaus]

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The issue

The release procedure contains references to landam/wingrass-maintenance-scripts, but it is not clear what needs to be updated and when.

Desired solution

The release procedure should include description of what files need to be changed for new release candidates, final releases, and new branches.

These changes can be done by the release manager of the given release as a PR against that repo.

Alternatives

These steps could be removed from the procedure because they go outside of the grass repo and OSGeo organization, but if all works as expected, they should be simple enough to do assuming it is really just adding few numbers here and there.

Ideally, at least parts of the winGRASS procedure would happen in the CI, but documenting the current procedure is easier and likely needed anyway for any larger changes.

Additional context

A similar procedure now works for the CI of the grass-addons repo where update is needed for new branches and that can be done using a PR and reviewed independently.

The document with the release procedure is here: https://github.com/OSGeo/grass/blob/main/doc/howto_release.md