GoUsers: add Maritime Optima AS

Also add instructions for updating the file
now that it's no longer a Github wiki.

Fixes golang/go#72865

Change-Id: Id820d6f69fc4938dc2c73ab22e275ea6700f44fa
Reviewed-on: https://go-review.googlesource.com/c/wiki/+/657855
Commit-Queue: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>