Make CommandAbstract a model

src/commands/view/CommandAbstract.js

@@ -1,7 +1,6 @@
-import Backbone from 'backbone';
-const $ = Backbone.$;
+import { Model } from 'backbone';
 
-export default Backbone.View.extend({
+export default Model.extend({
   /**
    * Initialize method that can't be removed
    * @param  {Object}  o Options

test/specs/grapesjs/headless.js

@@ -6,5 +6,6 @@ describe('GrapesJS Headless', () => {
   test('Can init editor', () => {
     const editor = grapesjs.init({ headless: true });
     expect(editor).toBeTruthy();
+    editor.destroy();
   });
 });