Support Non-Web WASM

[gkgoat1]

Description

WASM can run outside of the Web, and thus using winit there is impossible as the web target is hardcoded. I suggest having a "web" feature in the next breaking release and allowing users to customize what is used if that feature isn't set.

Relevant platforms

Web

[madsmtm]

I can see your point, technically someone could maybe implement Wayland WASM bindings?

I'm not aware of such a project though (are you?), so practically, there isn't anything else to use on WASM - so I'd rather keep it simple until that day comes. And if that day does come, we'll probably expose it by allowing you to use the winit-wayland crate on WASM.

In a similar vein, we only expose the option to use AppKit on macOS, even though one could theoretically use other windowing systems like X11, Wayland or SwiftUI.