create pull request template

Author: phip1611

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,7 @@
+*Descriptive summary of your bugfix, feature, or refactoring.*
+
+## Checklist
+- [ ] Sensible git history (for example, squash "typo" or "fix" commits): See the
+      [Rewriting History](https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History) guide for
+      help.
+- [ ] Update the changelog (if necessary)