Proj0300: Configure NuGet explicitly

The only way to ensure that NuGet is set up safely is by adding a NuGet.config file that is part of the source code. This prevents malicious configuration being present that is altered out of side in the global configuration.

Compliant

A NuGet.config file accessible to the project:

 <configuration>
  <packageSources>
    <clear />
    <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
</configuration>