Release v1.2.0

Summary

Prepares the publish workflows to move to the push trigger, which is what makes releases work for pull requests from forks.

Added

• reason output telling you why the action published nothing, so a workflow can fail on a release that went missing without failing on the ones that are expected.

Changed

• A commit that already has a release no longer publishes a second, higher version when its run is repeated (#103).
• Documented that cancel-in-progress: false is required under the push trigger.