typo: unkonw -> unknown

Author: nschonni

jsonschema-core.xml

@@ -382,7 +382,7 @@
                         authors can indicate what vocabularies are required or optional in
                         order to process the schema.  Since vocabularies are identified by URIs
                         in the meta-schema, generic implementations can load extensions to support
-                        previously unkonw vocabularies.  While keywords can be supported outside
+                        previously unknown vocabularies.  While keywords can be supported outside
                         of any vocabulary, there is no analogous mechanism to indicate individual
                         keyword usage.
                     </t>