feat: Create pull_request_template.md (#3268)

Adds a PR template as default PR description:

Hopefully this can also remind us to to keep docs up-to-date, as well,
like in #3263

---------

Signed-off-by: Ramon Petgrave <[email protected]>
Signed-off-by: Ramon Petgrave <[email protected]>
Co-authored-by: Ian Lewis <[email protected]>

Author: ramonpetgrave64

.github/pull_request_template.md

@@ -0,0 +1,15 @@
+# Summary
+
+...
+
+## Testing Process
+
+...
+
+## Checklist
+
+- [ ] Review the contributing [guidelines](./../CONTRIBUTING.md)
+- [ ] Add a reference to related issues in the PR description.
+- [ ] Update documentation if applicable.
+- [ ] Add unit tests if applicable.
+- [ ] Add changes to the [CHANGELOG](./../CHANGELOG.md) if applicable.