focusin: Added missing signature

Closes gh-760

Author: AurelioDeRosa

entries/focusin.xml

@@ -19,8 +19,11 @@
       <argument name="eventObject" type="Event" />
     </argument>
   </signature>
+  <signature>
+    <added>1.0</added>
+  </signature>
   <longdesc>
-    <p>This method is a shortcut for <code>.on('focusin', handler)</code>.</p>
+    <p>This method is a shortcut for <code>.on( "focusin", handler )</code> in the first two variations, and <code>.trigger( "focusin" )</code> in the third.</p>
     <p>The <code>focusin</code> event is sent to an element when it, or any element inside of it, gains focus. This is distinct from the <a href="/focus/">focus</a> event in that it supports detecting the focus event on parent elements (in other words, it supports event bubbling).</p>
     <p>This event will likely be used together with the <a href="/focusout/">focusout</a> event.</p>
   </longdesc>