Add WS_CLIPCHILDREN support for Windows in bevy_winit

[nicholasc]

What problem does this solve or what need does it fill?

The winit version used in Bevy now supports WS_CLIPCHILDREN for Windows. This is particularly useful when trying to render a Wry WebView for which the HTML content has a transparent background because it will prevent the Wry container from clipping the rendering surface used by Bevy. This is the last "obstacle" I see in order to fully/properly use HTML as a user interface layer for Bevy.

What solution would you like?

It could be to just add winit_window_attributes = winit_window_attributes.with_clip_children(false); here.
It could also be a more "configurable" approach using Window settings. Not sure considering this is Windows only.

What alternative(s) have you considered?

I don't really see any other alternatives.

Additional context

N/A