Add spinner to CSR UI loading message

app/owlca/templates/owlca/certificatesignrequest_create.html

@@ -29,7 +29,11 @@
 <script src="/static/react/main.js"></script>
 
 <h3 class="mt-3">Option A: Create CSR in your browser</h3>
-<div id="helper-root">Loading helper...</div>
+<div id="helper-root">
+  <div class="spinner-border" role="status">
+    <span class="sr-only">Loading helper...</span>
+  </div>
+</div>
 <script>
 keys.ReactDOM.render(
   keys.React.createElement(keys.CsrDialog, {