Mobile web text editing tracking issue

[emilk]

Text editing on mobile web is pretty bad in eframe.

• Top priority: On iOS safari, clicking a text field won't always bring up the on-screen keyboard #4569
• Backspace doesn't work in text edits on egui_web with virtual keyboards (on mobile) #1121
• text edit issues onscreen keyboard (web on android and native on android) #3802
• Focus tracking for input on web is janky #4571
• Text field is covered by keyboard on mobile web #4572
• Mobile keyboard should not behave like IME #4573

You can find eframe's web text input code in https://github.com/emilk/egui/blob/master/crates/eframe/src/web/text_agent.rs

[kud1ing]

• Maybe also iOS: Safari: TextEdit only receives a letter not the text completion #1752