Add Support for Fullscreen API

[Aalivexy]

Is your feature request related to a problem? Please describe. When I tried to use js in webview to make my app full screen, I found that I may need to manually implement UserEvents to make the external tao window full screen.

Describe the solution you'd like Provide optional Fullscreen API support or provide an example to make things like this easier

Describe alternatives you've considered none

Would you want to assign yourself to implement this feature?

• [ ] Yes
• [x] No

Additional context When I tried to implement the fullscreen function, I encountered the problem of calling the window library. (Also, Document.fullscreenElement cannot be changed by initialization_script or javascript) Is it possible to only full screen the webview regardless of where the webview is embedded?

[Aalivexy]

useful links: https://learn.microsoft.com/en-us/microsoft-edge/webview2/reference/win32/icorewebview2?view=webview2-1.0.664.37#add_containsfullscreenelementchanged