Check that release workflow is run on main (#1856)

* Announce whether the release script is running in dry_run mode or not

* Check that release is running in main branch

* Fix `run_name` -> `run-name`

* Import actions/github-script@v6 in main-branch-check

* Add missing `steps` attribute in main-branch-check

* Use `with` attribute with actions/github-script@v6

* Use single quotes instead of double quotes

* Use single quotes: "main" -> 'main'

* Add runs-on attribute