Add PR template

It was copied from Rust Driver repo, with "CONTRIBUTING.md" changed to
"CONTRIBUTING.rst".

Author: Lorak-mmk

.github/pull_request_template.md

@@ -0,0 +1,17 @@
+## Pre-review checklist
+
+<!--
+    Make sure you took care of the issues on the list.
+    Put 'x' into those boxes which apply.
+    You can also create the PR now and click on all relevant checkboxes.
+    See CONTRIBUTING.rst for more details.
+-->
+
+- [ ] I have split my patch into logically separate commits.
+- [ ] All commit messages clearly explain what they change and why.
+- [ ] I added relevant tests for new features and bug fixes.
+- [ ] All commits compile, pass static checks and pass test.
+- [ ] PR description sums up the changes and reasons why they should be introduced.
+- [ ] I have provided docstrings for the public items that I want to introduce.
+- [ ] I have adjusted the documentation in `./docs/source/`.
+- [ ] I added appropriate `Fixes:` annotations to PR description.