[clojure mode] Enable brace folding

Author: garug

mode/clojure/clojure.js

@@ -281,6 +281,7 @@ CodeMirror.defineMode("clojure", function (options) {
     },
 
     closeBrackets: {pairs: "()[]{}\"\""},
+    fold: "brace",
     lineComment: ";;"
   };
 });