add missing import to inputbar module

src/js/inputbar.js

@@ -1,6 +1,7 @@
-(function() {
 'use strict';
 
+import * as _ from "underscore";
+
 var weechat = angular.module('weechat');
 
 weechat.directive('inputBar', function() {
@@ -806,4 +807,3 @@ weechat.directive('inputBar', function() {
         }]
     };
 });
-})();