Add pull request template (#226)

Author: starryeyez024

.github/pull_request_templates/feature-branch.md

@@ -0,0 +1,23 @@
+## Feature Branch: Title
+
+* Appendix doc:
+    - 
+* Link(s) to demo pages_ where this element can be viewed:
+    - 
+
+### Ready-for-merge Checklist
+
+- [ ] Expected files: all files in the merge request related to one feature request?
+- [ ] Is your branch up-to-date with the master branch?
+- [ ] Did automated tests pass?
+- [ ] Was it [browser-tested](https://docs.google.com/spreadsheets/d/1luriPYswlGcKdcbKhQfW6kxIgj7tjNjnBVP7yZ4onwA/edit#gid=1660273076)?
+- [ ] Was this feature demo'd and the design review task marked as complete?
+- [ ] Did it get a LGTM *after the last commit*? (changelog updates are exempt from this rule)
+- [ ] Changelog: consider this your postage stamp, it can’t go out without one! Stories should be in alphabetical/numerical order under the tag release.
+
+
+---
+
+### What's in this branch?
+Summarize files edited as part of this MR along with a brief description of what was changed/why.
+