docs(angular.identity): add @param and @returns tags

Closes angular#10457

Author: zdlopez

src/Angular.js

@@ -403,6 +403,8 @@ noop.$inject = [];
        return (transformationFn || angular.identity)(value);
      };
    ```
+  * @param {*} value to be returned.
+  * @returns {*} the value passed in.
  */
 function identity($) {return $;}
 identity.$inject = [];