qnx6: credit contributor and mark filesystem orphan

Replace the content of the qnx6 README file with the canonical places for
such information.

Add the credits of the qnx6 contribution to CREDITS, and add an section in
MAINTAINERS to mark this filesystem as Orphan, as the domain ontika.net and
email address does not resolve to an IP address anymore.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20230220170210.15677-2-lukas.bulwahn@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>