Add complete support for .NET files

[massimilianokraus-kappas]

You should add support for these text files that are very used in every middle-to-big .NET project:

• .csproj (fundamental!)
• .sln (fundamental!)
• .nuspec
• .props
• .target
• .config

[smittytone]

I would need sample file content for any of these if I was to add support for them to PreviewCode.

[smittytone]

PS. Closing this thread and migrating it to the file-type request thread.