Add PyQt6 imports

[zjosua]

fixes #21

Description

Added PyQt6 imports, because Anki 23.10 will have Qt5 compat disabled by default.

Checklist:

• [x] I've read and understood the contribution guidelines
• [x] I've tested my changes against at least one of the following Anki builds:
  • [ ] Latest standard Anki 2.1 binary build
  • [ ] Latest alternative Anki 2.1 binary build
  • [x] Anki Version ⁨23.10 (23823d31)⁩ running from source
• [x] I've tested my changes on at least one of the following platforms:
  • [x] Linux, version: Debian 12
  • [ ] Windows, version:
  • [ ] macOS, version:
• [ ] My changes potentially affect non-desktop platforms, of which I've tested:
  • [ ] AnkiMobile, version:
  • [ ] AnkiDroid, version:
  • [ ] AnkiWeb

[khonkhortisan]

I'm confirming that this commit works on Anki 23.10 beta 6 on Windows 10 alongside all my other addons (and that what I wrote in #21 didn't work)

[dae]

Rather than version checks or try/except, you can just import from aqt.qt: https://addon-docs.ankiweb.net/qt.html#qt-versions

[glutanimate]

Thanks as always @zjosua! Switched to the aqt.qt shim in a quick follow-up commit.