Add a post deployment guide

Every deployments are unique and we always do new things for customers.
This is where we should put every configuration that we do for
customers.
This should act as a reminder for everyone that deploying a new
platform.

Closes: #5

Signed-off-by: Sébastien Han <sebastien.han@enovance.com>
What do you think about moving this section into a subsection of "deploy" itself?