[mode metadata] Add "cs" as alias for C#

Other places like discord, github and gitlab supports this.

Author: Logerfo

mode/meta.js

@@ -20,7 +20,7 @@
     {name: "C", mime: "text/x-csrc", mode: "clike", ext: ["c", "h", "ino"]},
     {name: "C++", mime: "text/x-c++src", mode: "clike", ext: ["cpp", "c++", "cc", "cxx", "hpp", "h++", "hh", "hxx"], alias: ["cpp"]},
     {name: "Cobol", mime: "text/x-cobol", mode: "cobol", ext: ["cob", "cpy"]},
-    {name: "C#", mime: "text/x-csharp", mode: "clike", ext: ["cs"], alias: ["csharp"]},
+    {name: "C#", mime: "text/x-csharp", mode: "clike", ext: ["cs"], alias: ["csharp", "cs"]},
     {name: "Clojure", mime: "text/x-clojure", mode: "clojure", ext: ["clj", "cljc", "cljx"]},
     {name: "ClojureScript", mime: "text/x-clojurescript", mode: "clojure", ext: ["cljs"]},
     {name: "Closure Stylesheets (GSS)", mime: "text/x-gss", mode: "css", ext: ["gss"]},