After commit 7df902b53c, the winit window
is not created when calling show() anymore but it's now created at
component creation time. That means the event loop workaround removed
in 459f810bd8 is now needed at
construction time.
Since this is a winit and wasm specific issue, it's now dealt with in
the wasm interpreter implementation, by invoking the creation from the
event loop from there and returning a promise in the API.
This changes the API therefore: create() can only be called after the
event loop is running.