add question about qt backends to PR tests
<!-- Please describe the tests that you ran to verify your changes. -->
- [ ] example: the test suite for my feature covers cases x, y, and z
- [ ] example: all tests pass with my change
+- [ ] example: I check if my changes works with both PySide and PyQt backends
+ as there are small differences between the two Qt bindings.
## Final checklist:
- [ ] My PR is the minimum possible work for the desired functionality
