Add missing line break

Author: graham-trott

presenter/index.html

@@ -10,7 +10,7 @@
       <b>JSON::Presenter</b><br>
       Click/Tap or key Space/RightArrow to start in manual mode<br>
       Click/Tap or key Space/RightArrow to advance<br>
-      Key Enter to start in auto mode
+      Key Enter to start in auto mode<br>
       Click/Tap to exit auto mode
     </div>
     <pre id="jp-script" style="display:none">https://cdn.jsdelivr.net/gh/easycoder/json-presenter/demo.json?v=200517</pre>