Edge: Inherit dark theme from Eclipse

[sratz]

Currently the WebView2 instances use COREWEBVIEW2_PREFERRED_COLOR_AUTO, i.e. they inherit the dark/light setting from the operating system, not the Eclipse application.

E.g., when setting the preferred app theme in Windows to 'light', but Eclipse to 'dark', the Edge browser will use 'light'.

It should however inherit from Eclipse and also use 'dark'.

To do this, the API https://learn.microsoft.com/en-us/microsoft-edge/webview2/reference/win32/icorewebview2profile#put_preferredcolorscheme needs to be implemented.