docs(guide/Data Binding): add heading to page

the other pages have one, this makes them look more unified.

Author: meldaravaniel

docs/content/guide/databinding.ngdoc

@@ -3,6 +3,8 @@
 @sortOrder 210
 @description
 
+# Data Binding
+
 Data-binding in Angular apps is the automatic synchronization of data between the model and view
 components.  The way that Angular implements data-binding lets you treat the model as the
 single-source-of-truth in your application.  The view is a projection of the model at all times.