Add C# to other languages.

doc/otherlang.md

@@ -22,6 +22,7 @@ project's documentation for details.
 ##### Serialization only
 
 * [C](https://github.com/jmckaskill/c-capnproto) by [@jmckaskill](https://github.com/jmckaskill)
+* [C#](https://github.com/mgravell/capnproto-net) by [@mgravell](https://github.com/mgravell)
 * [Go](https://github.com/glycerine/go-capnproto) by [@glycerine](https://github.com/glycerine) (originally by [@jmckaskill](https://github.com/jmckaskill))
 * [Java](https://github.com/dwrensha/capnproto-java/) by [@dwrensha](https://github.com/dwrensha)
 * [Javascript](https://github.com/popham/capnp-js-base) by [@popham](https://github.com/popham)