Refs #24928 -- Added introspection support for PostgreSQL JSONField

Thanks Adam Johnson and Tim Graham for the reviews.

docs/ref/django-admin.txt

@@ -366,7 +366,9 @@ output:
 * If ``inspectdb`` cannot map a column's type to a model field type, it'll
   use ``TextField`` and will insert the Python comment
   ``'This field type is a guess.'`` next to the field in the generated
-  model.
+  model. The recognized fields may depend on apps listed in
+  :setting:`INSTALLED_APPS`. For example, :mod:`django.contrib.postgres` adds
+  recognition for several PostgreSQL-specific field types.
 
 * If the database column name is a Python reserved word (such as
   ``'pass'``, ``'class'`` or ``'for'``), ``inspectdb`` will append

docs/releases/2.0.txt

@@ -123,6 +123,9 @@ Minor features
   operation installs the ``btree_gist`` extension to add support for operator
   classes that aren't built-in.
 
+* :djadmin:`inspectdb` can now introspect ``JSONField``
+  (``django.contrib.postgres`` must be in ``INSTALLED_APPS``).
+
 :mod:`django.contrib.redirects`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~