Add github pull request template

Primarily for a way to signal devs how to fix the code style, which the linter
might error out on.

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,15 @@
+## Summary
+<!-- Please provide an exhaustive description. -->
+
+## Type of change
+
+<!-- Please delete options that are not relevant. -->
+
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
+- [ ] This change requires a documentation update
+
+### Checklist
+- [ ] Existing tests have been adapted and/or new tests have been added
+- [ ] Code style has been fixed via `composer fix-tyle`