This commit implements a GitHub Action to update translation files with the PR automatically created on behalf of "github-actions[bot]", so that manual intervention and inflating activity of a committer is avoided. For now, only catalog templates (POT) files will be updated based on the master branch. When we start publishing translations, we can have the action build them.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>