I see there isn't a Qt example for waylandsink so I made one (for Qt5).
This MR has 2 commits:
- Commit 1: Create new subfolder "gtk" and move the current waylandsink example into it. No logic code changes.
- Commit 2: Add Qt example for waylandsink in subfolder "qt"
Tested on Fedora 35 with Qt 5.15.2 and GStreamer 1.20.