Fix submit button during submission and add accessibility helper

Signed-off-by: David Wallace <[email protected]>

Author: MyPyDavid

rdmo_chatbot/plugin/static/chatbot/css/copilot.css

@@ -59,6 +59,18 @@
     margin-right: .5rem;
 }
 
+.sr-only {
+    position: absolute;
+    width: 1px;
+    height: 1px;
+    padding: 0;
+    margin: -1px;
+    overflow: hidden;
+    clip: rect(0, 0, 0, 0);
+    white-space: nowrap;
+    border: 0;
+}
+
 /* remove the watermark at the bottom of the copilot */
 
 .watermark {