Migrate to PySide6

BUILDING.md

@@ -0,0 +1,12 @@
+# macOS
+
+nuitka --standalone --enable-plugin=pyside6 --macos-create-app-bundle --output-dir=build GDUtils.py
+
+# Windows
+
+nuitka --standalone --enable-plugin=pyside6 --windows-console-mode=disable --output-dir=build GDUtils.py
+
+# Linux
+
+nuitka --standalone --enable-plugin=pyside6 --output-dir=build GDUtils.py
+