Document WebView2/BlazorWebView/HybridWebView issues with Program Files

[jfversluis]

As per this issue: dotnet/maui#28792

I do think it might be a good idea to:

At minimum, MAUI should:
• Document that installing to Program Files is unsupported without additional configuration
• Provide an official workaround or default to a safe WebView2 setup on Windows

More information and a workaround is here: dotnet/maui#17827

But I think even mentioning that this might cause issues is good enough.