github template for PRs (#624)

Signed-off-by: Krasi Georgiev <kgeorgie@redhat.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+<!--
+    Don't forget!
+    
+    - Most PRs would require a CHANGELOG entry.
+    
+    - 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.
+    
+    - All exposed objects should have a comment.
+    
+    - All comments should start with a capital letter and end with a full stop.
+ -->