Add c# language docs

[kate-goldenring]

Add C# docs to language guide. Here is an example for C/C++: #147

[kate-goldenring]

@rajsite @dicej @bacongobbler tagging in case any of you have interest in taking this on

[bacongobbler]

I'd be interested in taking this one on once things have started to stabilize.

[rajsite]

A bytecode alliance blogpost went up yesterday on componentize-dotnet, Simplifying components for .NET/C# developers with componentize-dotnet which would be a good reference for writing a doc.

[bacongobbler]

I followed the blog post as written and ran into an issue. I'm following up with folks on discord. Once I have a working sample, I'll submit a PR.