font-viewer: Allow to compile with GTK3

However, drawing signal is disabled with GTK3. It need to be fixed later.
about-me: Add GTK3 support
accessibility: Add GTK3 support
common: Add GTK3 support
mouse: Add GTK3 support
default-applications: Add GTK3 support
keyboard: Add GTK3 support
keybindings: Add GTK3 support
appearance: Add GTK3 support
display: Add GTK3 support
windows: Add GTK3 support