Prettify the frontend code (#8648)

* Add Prettier global configs

* Format js/jsx/ts/tsx/less files

superset/assets/spec/javascripts/components/FormRow_spec.jsx

@@ -55,5 +55,4 @@ describe('FormRow', () => {
     expect(wrapper.find(Row)).toHaveLength(1);
     expect(wrapper.find(Col)).toHaveLength(2);
   });
-
 });