Bevy adapt desktop to mobile

When to use

Load this when a desktop window game must accept touch and a smaller layout. Platform features are on bevy-platform-mobile.

Input: touch and gestures features exist. Action mapping lives on bevy-input-handling.
UI: scale nodes with Node layout. Check the window docs for a dpi component before writing one. WindowResolution and scale-factor events exist on the window page (WindowScaleFactorChanged).
Textures: ASTC is mentioned only as a compression feature blurb.

Godot idea	Bevy idiom
Mouse	Touch feature. Check the input docs for pointer unification before writing it.
Hover menus	Replace hover-only actions. UI picking exists as `ui_picking`. Check that feature's docs for behavior before writing it.
Safe margins	Unverified.