Merge pull request #121 from cloudaper/deprecated-$schema

Update docs with deprecated version-less $schema

source/reference/schema.rst

@@ -17,19 +17,22 @@ It is recommended that all JSON Schemas have a ``$schema`` entry,
 which must be at the root.  Therefore most of the time, you'll want
 this at the root of your schema::
 
-    "$schema": "http://json-schema.org/schema#"
+    "$schema": "http://json-schema.org/draft/2019-09/schema#"
 
 Advanced
 --------
 
-If you need to declare that your schema was written against a specific version
-of the JSON Schema standard, you should include the draft name in the path, for
+You should declare that your schema was written against a specific version
+of the JSON Schema standard and include the draft name in the path, for
 example:
 
+- ``http://json-schema.org/draft/2019-09/schema#``
 - ``http://json-schema.org/draft-07/schema#``
 - ``http://json-schema.org/draft-06/schema#``
 - ``http://json-schema.org/draft-04/schema#``
 
+The possibility to declare ``$schema`` without specific version (``http://json-schema.org/schema#``) was deprecated after Draft 4 and should no longer be used.
+
 Additionally, if you have extended the JSON Schema language to include
 your own custom keywords for validating values, you can use a custom
 URI for ``$schema``.  It must not be one of the predefined values