Version 2.22.1 - Fix App Preferences not Saving

🐛 Bug Fixes

• Fix grouping: allow to group to "root" @amolenaar (#2884)
• Add support for dropping SysML diagrams on diagrams @amolenaar (#2883)
• Catch errors when a clipboard is empty @amolenaar (#2882)
• Fix DnD file opening on macOS @amolenaar (#2880)
• Fix wrong path in project flatpak manifest @danyeaw (#2877)
• Fix TypeError when changing to dark mode @amolenaar (#2875)

🧰 Maintenance

• Fix libadwaita 1.4.0 missing for hypothesis tests @danyeaw (#2881)
• Settings cleanup @amolenaar (#2879)
• Simplify GSettings schema self test @amolenaar (#2888)

Thanks again to @amolenaar and @danyeaw! 🎉