Moving how-to docs from docs.nuget.org
Moving how-to docs from docs.nuget.org

docs.nuget.org has had a docs page on Package Explorer, even though it's
not officially supported by nuget.org. Thus the appropriate home for
these docs is in the GitHub readme.md instead, so I've migrated that
content here.

campersau/NuGetPackageExplorer,NuGetPackageExplorer/NuGetPackageExplorer,NuGetPackageExplorer/NuGetPackageExplorer