Add pull request template

Author: Thierry Boileau

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,43 @@
+<!--
+  You are encouraged to remove irrelevant sections
+  They can't possibly apply to all cases
+-->
+
+## The aim
+
+<!--
+  Describe the goal of the PR, this should be functional only
+-->
+
+## The solution
+
+<!--
+  Explain the technical solution if relevant
+-->
+
+## Reproduction
+
+<!-- 
+  Help the reviewer do a functional test by adding any relevant information here
+  Can be a data set to import
+-->
+
+## Check-list
+
+<!-- 
+  Check that you didn't forget anything
+  Each item in the list below should have one child checked
+-->
+
+* PR size
+    * [ ] Under 300 lines :white_check_mark:
+    * [ ] Can't be split without complicating the process even more
+* Tests
+    * [ ] Added
+    * [ ] Not applicable (why?)
+* Doc
+    * [ ] Added
+    * [ ] Not applicable
+* Reviewer
+    * [ ] Asked for a review
+    * [ ] Added label `DO NOT REVIEW`