Add PR template

Signed-off-by: Richard Hartmann <richih@richih.org>

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,15 +1,17 @@
 <!--
     Don't forget!
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+    - Sign your commits and our DCO:  https://docs.github.com/en/github/authenticating-to-github/managing-commit-signature-verification/signing-commits
+
     - If the PR adds or changes a behaviour or fixes a bug of an exported API it would need a unit/e2e test.
-    
+
     - Where possible use only exported APIs for tests to simplify the review and make it as close as possible to an actual library usage.
-    
+
     - No tests are needed for internal implementation changes.
-    
+
     - Performance improvements would need a benchmark test to prove it.
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+
     - All exposed objects should have a comment.
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+
     - All comments should start with a capital letter and end with a full stop.
- -->
+ -->