Doc: Describe model and state chart wizards

Add the Qt SCXML index file to be able to link to the module
docs.

Change-Id: Ibd28071cdc3c98c07fb91c73732d809ffed5333b
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

doc/config/qtcreator-project.qdocconf

@@ -42,6 +42,7 @@ indexes +=    $QDOC_INDEX_DIR/qtwidgets/qtwidgets.index \
               $QDOC_INDEX_DIR/qtquicklayouts/qtquicklayouts.index \
               $QDOC_INDEX_DIR/qtlinguist/qtlinguist.index \
               $QDOC_INDEX_DIR/qtscript/qtscript.index \
+              $QDOC_INDEX_DIR/qtscxml/qtscxml.index \
               $QDOC_INDEX_DIR/qtsensors/qtsensors.index \
               $QDOC_INDEX_DIR/qttestlib/qttestlib.index \
               $QDOC_INDEX_DIR/qtuitools/qtuitools.index \

doc/src/projects/creator-projects-creating.qdoc

@@ -314,6 +314,23 @@
 
         \endlist
 
+        \li Models and state charts
+
+        \list
+
+            \li Universal Modeling Language (UML) style models with structured
+                diagrams. However, the model editor uses a variant of UML and
+                provides only a subset of properties for specifying the
+                appearance of model elements. For more information, see
+                \l {Modeling}.
+
+            \li State Chart XML (SCXML) files that contain boilerplate code for
+                state machines. You can use the classes in the \l {Qt SCXML}
+                module to embed state machines created from the files in Qt
+                applications.
+
+        \endlist
+
         \li GLSL
 
             GLSL files that define fragment and vertex shaders in both Qt Quick