update prelease sample app 

update Testing-Instructions.md 

Update README.md 

Updates for Win32, WPF and WinForms sample apps for 1.0.901-prerelease 

Snapshot for 1.0.864.35 testing 

update launch.json with corrected paths 

Win32, WPF, Winforms sample apps work with 1.0.865-prerelease 

Revert packages.config 

Update the sample apps. Win32 works with 1.0.818.41-prerelease WPF and WinForms work with 1.0.818.41

Update projects to use the latest WebView2 SDK 1.0.824-prerelease