Add pull request templates

Author: AHarmlessPyro

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+## Summary
+<!-- 1-2 sentences: what changed and why. -->
+
+## Changes
+<!-- Bullet list of the concrete changes. Keep it short. -->
+- 
+- 
+
+## Validation
+<!-- Commands you ran. Mention any manual testing. -->
+- `yarn lint`
+- `yarn build`
+
+<!-- Closes #123 -->