Keyboard/mouse state for this tick — inserted as a resource by
WindowPlugin. key_pressed/mouse_pressed are edge-triggered (true
only the tick a key/button went down); key_held/mouse_held are
level-triggered (true for as long as it’s down).
Opens a window (via winit) and inserts Window/Input as
resources. Installs a runner that drives the app from winit’s own
event loop — functional on native and wasm32-unknown-unknown.