Only schedule frame callback from on_process
draw was called in the pipewire on_process callback, but this is not
safe as libpipewire runs on_process on a separate thread.
Instead, kickstart a frame callback loop if needed and let the
Wayland-side drive drawing on the main thread.
readme: Update discuss section
Move peak_decay to input side
Move display_dispatch closer to use
Switch from EGL to software rendering
Swap ALSA out with PipeWire
layer-shell: Use bottom layer
readme: Elaborate on function