title: Option "Add NuGet packages" not available/greyed out
body: <p>When I create a Xamarin forms project in Visual Studio for Mac, the option "Add NuGet packages" is not available:</p>
  
  <p><a href="https://i.stack.imgur.com/2VSe0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2VSe0.png" alt="enter image description here"></a></p>
  
  <p>I need it to add JSON and HTTP packages.
  The project is not running or in debug mode, and I already tried to restart the project, but that didn't help. Any idea why it is not available?</p>