Add cake-module tag to Cake.DNF.Module NuGet package

[augustoproiete]

The NuGet Gallery will soon include a "Cake" tab with instructions on how to use NuGet packages in Cake build scripts. I'd like to suggest that you include the tag cake-module in the NuGet package of this module, so that the NuGet Gallery can display the correct instructions to install this module.

The UI will look similar to this:

Documentation on best practices on tags for Cake modules: https://cakebuild.net/docs/extending/modules/best-practices#tags