📝 Add NuGet metadata

[Mattias1]

✨ What's this?

Add some metadata for the NuGet gallery (https://www.nuget.org/packages/Bearded.Utilities).
Specifically, a link back to the github repo, a MIT licence and a good description.

🔍 Why do we want this?

More clarity for people using the NuGet gallery.

🏗 How is it done?

Mostly moving metadata from the (no longer used) nuspec file to the project file, as is the best practice these days (https://learn.microsoft.com/en-us/nuget/create-packages/package-authoring-best-practices).

🔬 Why not another way?

It's best practice these days to use the project file instead of nuspec files (which you weren't using anymore anyways).

🦋 Side effects

Maybe the tags aren't up to date anymore?

[Mattias1]

I cannot add labels myself, can you add ignore-for-release here? I think it applies.