Always include check for webview

[dotMorten]

In all the examples, please include the code to handle a check for whether the webview2 control is installed or not. I don't really see any examples of how to handle this scenario. I do see issues people have logged not being able to get the sample to work because they didn't install the runtime.

[champnic]

Thanks for the request @dotMorten - I've added a bug on our backlog to track this.