Adds permitted feature #scriptEventGrouping (#238)

Closes #237 .

* Adds permitted feature `#scriptEventGrouping`
* Add at-risk features `#scriptEventGrouping` and `#scriptEventMapping`
* Adds link to at-risk feature logged in #239.

index.html

@@ -263,6 +263,7 @@ <h1 id="title">Dubbing and Audio description Profiles of TTML2</h1>
         <div class="issue" data-number="222"></div>
         <div class="issue" data-number="223"></div>
         <div class="issue" data-number="224"></div>
+        <div class="issue" data-number="239"></div>
 
         <p><a>At risk</a> features may be be removed before advancement to Proposed Recommendation.</p>
     </section>
@@ -3196,6 +3197,14 @@ <h4>Disposition of Features and Extensions</h4>
               This is the profile expression of <a href="#represents"></a>.
             </td>
           </tr>
+          <tr>
+            <td><a href="#scripteventgrouping"><code>#scriptEventGrouping</code></a></td>
+            <td><span class="permitted label">permitted</span></td>
+            <td>
+              This is the profile expression of the permission to nest
+              <code>&lt;div&gt;</code> elements described in <a href="#script-event"></a>.
+            </td>
+          </tr>
           <tr>
             <td><a href="#scripteventmapping"><code>#scriptEventMapping</code></a></td>
             <td><span class="optional label">optional</span></td>
@@ -3378,6 +3387,20 @@ <h3>#represents-root</h3>
           or has one whose value is not conformant with the requirements defined herein.</p>
       </section>
 
+      <section>
+        <h3>#scriptEventGrouping</h3>
+        <p>A <a>transformation processor</a> supports the <code>#scriptEventGrouping</code> extension if
+          it recognises and is capable of transforming <code>&lt;div&gt;</code> elements
+          that contain <code>&lt;div&gt;</code> elements.</p>
+
+        <p class="note">Support for the <code>#scriptEventGrouping</code> extension does not imply
+          support for the <code>#scriptEventMapping</code> extension.</p>
+
+        <p>A <a>presentation processor</a> supports the <code>#scriptEventGrouping</code> extension if
+          it implements presentation semantic support for <code>&lt;div&gt;</code> elements
+          that contain <code>&lt;div&gt;</code> elements.</p>
+      </section>
+
       <section>
         <h3>#scriptEventMapping</h3>
         <p>A <a>transformation processor</a> supports the <code>#scriptEventMapping</code> extension

profiles/dapt-content-profile.xml

@@ -91,6 +91,7 @@
     <!-- optional (voluntary) extension support -->
     <extension value="optional">#agent</extension>
     <extension value="optional">#onScreen</extension>
+    <extension value="optional">#scriptEventGrouping</extension>
     <extension value="optional">#scriptEventMapping</extension>
     <extension value="optional">#textLanguageSource</extension>
     <!-- prohibited extension support -->

profiles/dapt-processor-profile.xml

@@ -86,6 +86,7 @@
     <extension value="required">#contentProfiles-root</extension>
     <extension value="required">#onScreen</extension>
     <extension value="required">#represents-root</extension>
+    <extension value="required">#scriptEventGrouping</extension>
     <extension value="required">#scriptType-root</extension>
     <extension value="required">#serialization</extension>
     <extension value="required">#textLanguageSource</extension>