message: Added a missing extension point to documentation.
  Commit Message: Updated the extending envoy documentation to include a missing extension point.
  Additional Description: See PR for additional context of this.
  Risk Level: low
  Testing: built the documents to ensure they generate correctly.
  Docs Changes:
  Release Notes:
diff: @@ -21,6 +21,7 @@ types including:
  * :ref:`Request ID <arch_overview_tracing>`
  * Transport sockets
  * BoringSSL private key methods
  +* :ref:`Internal redirect policy <envoy_v3_api_field_config.route.v3.InternalRedirectPolicy.predicates>`
  As of this writing there is no high level extension developer documentation. The
  :repo:`existing extensions <source/extensions>` are a good way to learn what is possible.
  