Update docs - Add C# SDK (modelcontextprotocol#207)

* Update docs.json - Include C#

* Move down per order of appearance

---------

Co-authored-by: David Soria Parra <[email protected]>

Author: stvansolano

docs.json

@@ -96,6 +96,11 @@
           "href": "https://github.com/modelcontextprotocol/kotlin-sdk",
           "icon": "square-k"
         },
+        {
+          "anchor": "C# SDK",
+          "href": "https://github.com/modelcontextprotocol/csharp-sdk",
+          "icon": "square-c"
+        },
         {
           "anchor": "Specification",
           "href": "https://spec.modelcontextprotocol.io",