antlr/.github/PULL_REQUEST_TEMPLATE.md

Thank you for proposing a contribution to the ANTLR project. In order to accept changes from the outside world, all contributors most "sign" the contributors.txt contributors certificate of origin. It's an unfortunate reality of today's fuzzy and bizarre world of open-source ownership.

Make sure you are already in the contributors.txt file or add a commit to this pull request with the appropriate change. Thanks!