Install unlisted Nuget packages

[tareqimbasher]

Discussed in https://github.com/tareqimbasher/NetPad/discussions/308

^{Originally posted by RThomasHyde March 19, 2025} I work with vendors who sometimes supply hotfix Nuget packages for testing. These packages are hidden from the Nuget feed (they don't even show up in the prerelease channel), I have to install them with the -v flag for the specific hotfix version. If there was a way that I could install a specific (unlisted) nuget package version in Netpad it would make testing these hotfixes a little bit easier.