Provider for creating
Revolves a webview view.
resolveWebviewView is called when a view first becomes visible. This may happen when the view is
first loaded or when the user hides and then shows a view again.
Webview view to restore. The provider should take ownership of this view. The
provider must set the webview's
.html and hook up all webview events it is interested in.
Additional metadata about the view being resolved.
Cancellation token indicating that the view being provided is no longer needed.
Optional thenable indicating that the view has been fully resolved.