feat: define application life-cycle task source (#518)

Author: Marcos Cáceres

index.html

@@ -330,7 +330,7 @@ <h3>
               populate an <a>installation process</a>' UI.
               </li>
               <li>If the <a>installation succeeded</a>, <a>queue a task</a> on
-              the <dfn>application life-cycle task source</dfn> to <a>fire an
+              the <a>application life-cycle task source</a> to <a>fire an
               event</a> named <code>appinstalled</code> at the
               <var>window</var> object.
               </li>
@@ -408,6 +408,10 @@ <h3>
       <h2>
         Installation Events
       </h2>
+      <p>
+        DOM events <a>fired</a> by this specification use the <dfn>application
+        life-cycle task source</dfn>.
+      </p>
       <section>
         <h3>
           Extensions to the <code>Window</code> object