[mod] link to public-instances can be set to hidden

Some administrators may want to hide the link to public_instances: If you run a
private instance for a company that wants there employees to use the private
instance instead of any of the public instances.

AUTHORS.rst

@@ -164,3 +164,4 @@ features or generally made searx better:
 - @OliveiraHermogenes
 - Paul Alcock @Guilvareux
 - Sam A. `<https://samsapti.dev>`_
+- @XavierHorwood