[Feature] Update nuspec file

[haavamoa]

Hi, thank you for delivering such a great and simple to use tool for managing dependencies.👍

It would be amazing if I could update dependencies and update my nuspec at the same time.
Some of us are still using nuspec files to manage our nuget packages (like this one), and making sure our dependencies are in sync with the csproj can be a nightmare.

Love the tool, keep up the good work!

[haavamoa]

#5 Thanks a lot @seesharper <3