Use EventLoopExtWebSys::spawn in bevy_winit

[allsey87]

See rust-windowing/winit#1714 for the relevant discussion, but the TLDR is that EventLoopExtWebSys::spawn provides a work around for the hack of using an exception to get the event loop working on the web platform.

rust-windowing/winit#2208 is included in winit 0.27.0 which is included in Bevy 0.9, however, bevy_winit is current not using this feature.

Other related issues: rust-windowing/winit#900 rust-windowing/winit#1199

[allsey87]

I haven't investigated this yet, but @bjorn3 pointed out the following on Discord:

It (EventLoopExtWebSys::spawn) also isn't compatible with the App::run interface as App::run allows dropping the App after it returns