Add a C# coder

[joshsh]

It is quite possible that an entire Hydra-Csharp implementation will be required. In the meantime, the ability to transform type definitions into C# will be helpful.

[joshsh]

An up-to-date, though not explicitly dated, C# grammar is here: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/grammar

[joshsh]

The branch has been deleted to avoid future conflicts. Work on the C# coder is also halted for the time being. However, the existing C# sources have been merged into main.

[joshsh]

Closing; C# support is not a priority at this time.