add WguiFontSystem, remove FONT_SYSTEM singleton, custom fonts, add Light font weight

there are a few gzip-compressed ttf as for now, looks like variable fonts aren't parsed properly by cosmic_text. Not sure why. Also, we probably need to have a fallback for CJK characters in the future, or just fallback to the built-in ones in the OS.

wgui/src/components/mod.rs

@@ -17,6 +17,7 @@ pub struct InitData<'a> {
 // common component data
 #[derive(Default)]
 pub struct ComponentBase {
+	#[allow(dead_code)]
 	lhandles: Vec<EventListenerID>,
 }