Explain how to configure organizations and environments in APIM Gateway gravitee.yml

[plsstephenson]

The Cockpit doc introduction explains that it's possible to configure the organizations and environments for an APIM Gateway in gravitee.yml. Ilies is investigating a scenario for this, which will need adding to the APIM Gateway general config, linked from the Cockpit doc.

[plsstephenson]

See the Installation / Node entry in the Cockpit hierarchy table here: https://docs.gravitee.io/cockpit/3.x/cockpit_overview_introduction.html
This gives general info about configuring APIM Gateway, but no scenario for configuring organizations and environments.
TBD - if this also applies to AM organizations and environments, and whether to add this to the Cockpit doc or the APIM/(and AM) doc