Merge pull request #886 from p12tic/github-pr-template

github: Add PR template

Author: p12tic

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,7 @@
+
+## Contributor Checklist:
+
+If this PR adds a new feature that improves compatibility with docker-compose, please add a link
+to the exact part of compose spec that the PR touches.
+
+All changes require additional unit tests.