Add author/paper id help text for invited speakers

Change-Id: Ib3bdcac296c9761fd21b4b9e330fdf8c6d92e1d2
diff --git a/templates/register.htm b/templates/register.htm
index e92b69b..268979c 100644
--- a/templates/register.htm
+++ b/templates/register.htm
@@ -457,6 +457,9 @@
             <label class="form-check-label fs-4" for="author">I am an author of a paper accepted for the conference.
             </label>
         </div>
+        <div id="authorHelp" class="form-text">
+            Invited speakers should leave this box unchecked.
+        </div>
     </div>
 
     <div class="form-outline col-md-5">