Fixed #21154 -- Updated TemplateResponse docs to better explain context.

Thanks mrmachine for the report.

docs/ref/template-response.txt

@@ -132,10 +132,10 @@ TemplateResponse objects
 
 .. class:: TemplateResponse()
 
-   TemplateResponse is a subclass of
-   :class:`~django.template.response.SimpleTemplateResponse` that uses
-   a :class:`~django.template.RequestContext` instead of
-   a :class:`~django.template.Context`.
+    ``TemplateResponse`` is a subclass of
+    :class:`~django.template.response.SimpleTemplateResponse` that uses
+    a :class:`~django.template.RequestContext` instead of
+    a :class:`~django.template.Context`.
 
 Methods
 -------
@@ -155,7 +155,9 @@ Methods
     ``context``
         A dictionary of values to add to the template context. By default,
         this is an empty dictionary. :class:`~django.template.Context` objects
-        are also accepted as ``context`` values.
+        are also accepted as ``context`` values. If you pass a
+        :class:`~django.template.Context` instance or subclass, it will be used
+        instead of creating a new :class:`~django.template.RequestContext`.
 
     ``status``
         The HTTP Status code for the response.