Add PR template (#45)

Self-explanatory.

Author: IshaanDesai

.github/pull_request_template.md

@@ -0,0 +1,8 @@
+<!-- Add a short description of your contribution here. Skip this if the title is self-explanatory -->
+
+Checklist:
+
+- [ ] I made sure that the CI passed before I ask for a review.
+- [ ] I added a summary of the changes (compared to the last release) in the `CHANGELOG.md`.
+- [ ] If necessary, I made changes to the documentation and/or added new content.
+- [ ] I will remember to squash-and-merge, providing a useful summary of the changes of this PR.