Support Multiple Nuget Feeds

You can set an alternative feed, but this only supports changing the feed.

It would be nice to be able to specify multiple nuget feeds.

Or, even better use the nuget.config file that projects use.

Start by locating the existing alternative-feed option and tracing how package feeds are read for .NET projects. Compare the desired behavior with standard nuget.config usage and determine whether multiple feeds, nuget.config discovery, or both are in scope; done means projects can resolve packages from the supported feed configuration.

Written by the indexing model from the issue text.