Update screenshots

Tested self contained executable
as per https://learn.microsoft.com/en-us/dotnet/core/deploying/single-file/overview?tabs=vs

Added option new Cleanup command which delete old version files and f…

…older using CLI --clean parameter.

Upgraded Newtonsoft.Json version

Update README.md

Upgraded to .Net Core 3.1

Upgraded packages.config
Removed dependency on WindowsAPICodePack

Update README.md

Updated changed workload url

Added support for Proxy.

Incremented version to 1.3

Removed Prism dependency,

Added Archive folder to Old Version Module List for deletion,
Added Potential fix for Old Version Module List still show old files which were deleted when navigated back and forth

Added Download Utility screenshot

Merge branch 'master' of https://github.com/deepak-rathi/VS2017Offlin…

…eSetupUtility