merlin.cfg: New game IP.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
(cherry picked from commit 6d4e5817dfb946ebaa232f991172d3857e9d5a15)
README: Added config-desc.md.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
(cherry picked from commit 3840484e9f6fe4c3e4398f8cabb2a516cf457c6e)