Add namespace descriptions to docs

[JamesNK]

There are no namespace descriptions in Aspire API docs. See https://learn.microsoft.com/en-us/dotnet/api/?view=dotnet-aspire-9.3

Compare with .NET which does have namespace descriptions: https://learn.microsoft.com/en-us/dotnet/api/?view=net-10.0

Things might have changed, but this issue talks about what is required last time I looked at API docs namespace descriptions: dotnet/aspnetcore#27286