Small quality of life improvements and minor bug fixes:
- feat: prevent launching multiple instances (#82)
- feat: add a tray icon (#2)
- feat: allow minimising the app to the tray
- feat: allow zooming in with "CTRL + =" (#8)
- fix: artifact like shapes on start (#57)
- feat: add spell check
- fix: bundle window icon correctly
- feat(ci): generate DMG rather than ZIP
