webview_create
Creates a new webview instance.
If debug is non-zero - developer tools will be enabled (if the platform supports them). Window parameter can be a pointer to the native window handle. If it's non-null - then child WebView is embedded into the given parent window. Otherwise, a new window is created. Depending on the platform, a GtkWindow, NSWindow or HWND pointer can be passed here.
Return
a webview handle