Intellisense docs not being packaged into NuGet

[DrEsteban]

I'm not really sure why, but for some reason the Intellisense documentation in this repo isn't making it into the final NuGet package.

E.g. https://github.com/dasiths/NEasyAuthMiddleware/blob/master/NEasyAuthMiddleware/Core/EasyAuthOptions.cs#L9-L12

[DrEsteban]

Looking around briefly, I wonder if something like this is necessary in the csproj?

<PropertyGroup>
    <GenerateDocumentationFile>true</GenerateDocumentationFile>
  </PropertyGroup>

And/or, including symbols in the package?