.github/workflows/autobranch.yml: Add "master" autobranch
Now that we have transitioned from "master" to "main" branch, add a "master" autobranch that will track "main" with extra warnings in the doc, the code and the shell scripts.
GitLab Maintenance scheduled for Thursday, 18th December 2025, from 7:00 AM to 10:00 AM BST. GitLab will be in read-only mode and experience short periods of complete downtime (up to 20 minutes) during this window.
Now that we have transitioned from "master" to "main" branch, add a "master" autobranch that will track "main" with extra warnings in the doc, the code and the shell scripts.