Improve comments component

app/javascript/components/shared/Spinner.tsx

@@ -1,7 +1,7 @@
 import * as React from 'react';
 
 const Spinner = () => (
-  <div className="spinner-border d-block mx-auto" role="status">
+  <div className="spinner-grow d-block mx-auto" role="status">
     <span className="sr-only">Loading...</span>
   </div>
 );