Add GitHub PR Template (#239)

* Add PR template as we've done many times in the rest of our projects

* Update PULL_REQUEST_TEMPLATE.md

PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,20 @@
+### :pushpin: References
+* **Issue:** _your issue goes here_
+* **Related pull-requests:** _list of related pull-requests (comma-separated): #1, #2_
+
+### :tophat: What is the goal?
+
+_Provide a description of the overall goal (you can usually copy the one from the issue)_
+
+### :memo: How is it being implemented?
+
+_Provide a description of the implementation_
+
+### :robot: How can it be tested?
+
+_If it cannot be tested explain why._
+
+- [ ] **Use case 1:** _A brief description of the use case that should be tested_
+- [ ] **Use case 2:** _If the use case requires some complex steps, increase indentation_
+  - [ ] _Step 1_
+  - [ ] _Step 2_