Update PR template

Author: joepio

pull_request_template.md

@@ -1,6 +1,6 @@
 PR Checklist:
 
-- [ ] Link to related issue
-- [ ] Add changelog entry linking to issue
-- [ ] Added tests (if needed)
-- [ ] (If new feature) added in description / readme
+- [ ] Link to related issues: #number
+- [ ] Add changelog entry linking to issue, describe API changes
+- [ ] Add tests (optional)
+- [ ] (If new feature) add to description / readme