Extend touchpad magnify and rotate gestures support to Web

[megaboy101]

Hey all,

I recently ran into an issue where I wanted to add two-finger pinch/zoom to a webassembly-compiled Bevy app I was building.

However it looks like magnify and rotate gesture recognition is currently limited to MacOS (#2157).

I'm not too familiar with Winit's internals, but I'd be interested in adding a webassembly implementation to support these gesture events if possible.

[daxpedda]

Hm, I'm not sure we should, it's not supported but we could polyfill it of course. See the MDN documentation on how to polyfill this.

Safari has actually a dedicated API (MDN) for it, which we could definitely implement.

@kchibisov do we intend to polyfill this for other targets too if they don't have official support for it? I saw in #2157 that Wayland and Windows support it, does X11 support it?

[kchibisov]

I think X11 should also support this, it's all coming from the libinput.

[daxpedda]

Alright, let's just go ahead with this then.

@megaboy101 PR's are welcome, I'm happy to review one. Feel free to ping if you need any guidance!