Added coding style modes to SimpleMDE (#3286)

* Added coding style modes to SimpleMDE

* Moved the CodeMirror addon from simplemd to codemirror directory

public/plugins/codemirror-5.17.0/mode/css/gss_test.js

@@ -0,0 +1,17 @@
+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: http://codemirror.net/LICENSE
+
+(function() {
+  "use strict";
+
+  var mode = CodeMirror.getMode({indentUnit: 2}, "text/x-gss");
+  function MT(name) { test.mode(name, mode, Array.prototype.slice.call(arguments, 1), "gss"); }
+
+  MT("atComponent",
+     "[def @component] {",
+     "[tag foo] {",
+     "  [property color]: [keyword black];",
+     "}",
+     "}");
+
+})();