[css-gcpm-3] add break-before properties to examples 13 and 14 to trigger page group creation, per w3c#3524

Author: dauwhe

css-gcpm-3/Overview.bs

@@ -736,8 +736,14 @@ NOT TRUE; NEED TO DESCRIBE
 CSS:
 
 <pre>
-div { page: A }
-child { page: B }
+div { 
+  page: A;
+  break-before: always;
+}
+child { 
+  page: B;
+  break-before: always;
+}
 </pre>
 <figure>
 <img src="images/PageGroups.001.jpg" width="480" alt=""/>
@@ -784,11 +790,13 @@ And CSS:
 
 <pre>
 div.chapter {
-page: body;
+  page: body;
+  break-before: always;
 }
 
 table.broadside {
-page: broadside;
+  page: broadside;
+  break-before: always;
 }
 
 </pre>