Add information about managing multiple rule sets

[approksiu]

Consider adding an FAQ item to answer question: "How do I manage a few different rule sets (eg from different spaces/ for different customers) with the repo"?

• What needs to be considered in the setup config, workflows etc?
• How to easily automate sync from multiple spaces? and to multiple spaces?

[eric-forte-elastic]

We should also include better usage information around using filters such as https://www.elastic.co/docs/api/doc/kibana/operation/operation-findrules#operation-findrules-filter to manage multiple rule sets as this is a common technique to use in CI. This should include information such as ref.