Android: set KeyEvent::text if possible

[podusowski]

Related discussion: #3787 (comment)

• Tested on all platforms changed
• Added an entry to the changelog module if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

[Zoxc]

This change does make some text input with the software keyboard possible with egui. Android seems to emulate physical keys when a proper IME connection is missing.