RELEASING.md

Releasing the Terraform provider

1. Merge all your changes to the stable branch
2. Create a new release branch e.g. release-v2.3.5
3. Update CHANGELOG.md
   1. Add new heading with the correct version e.g. ## [2.3.5]
   2. Update links at the bottom of the page
   3. Leave "Unreleased" section at the top empty
4. Update galaxy.yml with the new version
5. Update README.md's download link with the new version
6. Merge your release branch to the stable branch
7. Create and push a new tag e.g v2.3.5
8. GitHub actions will trigger on tag and do a build & release of the tagged version
9. Check the release page for the release
10. Add correct changelog to the release if it's missing
11. Done!