Add window_set_fullscreen Window API

[wusyong]

This is the first attempt to introduce a window api structure start with setting fullscreen.
Users can get the window handle from webview_get_window() and use it with any window api with prefix of window_*.

[d1y]

Thank you

[vikigenius]

Is there anything blocking this from merging ? This is a very nice feature to have.

[nothingismagick]

Good question, I agree would be great to merge in. Any blockers @wusyong ?

[wusyong]

It's probably not compatible with m1. I'll update it later.

[abemedia]

Would be great to also have Go bindings for this.

[dumanhaydar]

When I try, I have this error :

In file included from webview.cc:3:
./webview.h:577:10: error: no matching function for call to 'objc_msgSend'

[dumanhaydar]

And on Windows:

c:/mingw/bin/../lib/gcc/x86_64-w64-mingw32/11.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: $WORK\b001\_x002.o: in function `_cgo_5d5d1491a383_Cfunc_window_set_fullscreen':
/tmp/go-build/cgo-gcc-prolog:248: undefined reference to `window_set_fullscreen'