Added pull request template (#1436)

Author: jar-stripe

.github/pull_request_template.md

@@ -0,0 +1,11 @@
+### Why?
+<!-- Describe why this change is being made.  Briefly include history and context, high-level what this PR does, and what the world looks like afterward. -->
+
+### What?
+<!--
+List out the key changes made in this PR, e.g.
+- implements the antimatter particle trace in the nitronium microfilament drive
+- updated tests -->
+
+### See Also
+<!-- Include any links or additional information that help explain this change. -->