Implemented all of uiCheckbox on GTK+.
Implemented all of uiCheckbox on GTK+.

cainiaocome/ui,mirrr/ui,ProtonMail/ui,292388900/ui,HunterChen/ui,ProtonMail/ui,HunterChen/ui,cainiaocome/ui,janstk/ui,hajimehoshi/ui,cainiaocome/ui,292388900/ui,mirrr/ui,292388900/ui,beni55/ui,hajimehoshi/ui,ProtonMail/ui,janstk/ui,robbiev/ui,beni55/ui,mirrr/ui,hajimehoshi/ui,janstk/ui,robbiev/ui,robbiev/ui,beni55/ui,HunterChen/ui