Documentation - add StreamFieldPanel to available panel types

docs/reference/pages/panels.rst

@@ -28,6 +28,23 @@ FieldPanel
 
         This parameter allows you to specify a :doc:`Django form widget <django:ref/forms/widgets>` to use instead of the default widget for this field type.
 
+StreamFieldPanel
+----------------
+
+.. class:: StreamFieldPanel(field_name, classname=None, widget=None)
+
+    This is the panel used for Wagtail's StreamField type (see :ref:`streamfield`).
+
+    .. attribute:: FieldPanel.field_name
+
+        This is the name of the class property used in your model definition.
+
+    .. attribute:: FieldPanel.classname (optional)
+
+        This is a string of optional CSS classes given to the panel which are used in formatting and scripted interactivity. By default, panels are formatted as inset fields.
+
+        The CSS class ``full`` can be used to format the panel so it covers the full width of the Wagtail page editor.
+
 MultiFieldPanel
 ---------------