ci: add PR template

Author: rawqubit

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+## Summary
+
+<!-- What does this PR do? -->
+
+## Type of change
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Breaking change
+- [ ] Documentation update
+
+## Checklist
+- [ ] Tests added / updated (`pytest tests/`)
+- [ ] CHANGELOG.md updated
+- [ ] README updated if needed