Add json example for nested object in the doc

[zodd3131]

Describe the feature
A new feature has been added that provides the ability to pass broker.properties through a json secret.
ActiveMQArtemisSecurity is now a deprecated resource and it's now recommanded to provide configuration with spec.brokerProperties. I would like to implement what it is described here : providing-additional-brokerproperties-configuration-from-a-secret).
How to write nested object and what to escape as characters?
How to translate the yaml below into a json secret?

securitySettings:
    broker:
      - match: "app.europe.#"
        permissions:
          - operationType: createNonDurableQueue
            roles: ["admin"]
          - operationType: deleteNonDurableQueue
            roles: ["admin"]
          - operationType: createDurableQueue
            roles: ["admin"]
          - operationType: deleteDurableQueue
            roles: ["admin"]
          - operationType: createAddress
            roles: ["admin"]
          - operationType: deleteAddress
            roles: ["admin"]
          - operationType: createAddress
            roles: ["admin"]
          - operationType: consume
            roles: ["admin", "guest"]
          - operationType: send
            roles: ["admin"]

I would like to complete the documentation with more complex examples.

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