Update networking instructions for ESPHome

[FuNK3Y]

Description:

Document the new env variable that allow to specify a listening network interface for the dashboard

Pull request in esphome with YAML changes (if applicable):

• https://github.com/esphome/esphome/pull/11876

Checklist:

• [X] I am merging into next because this is new documentation that has a matching pull-request in esphome as linked above.

I did purposely not prefix the env var with esphome like the other - as this one does not alter the behavior or esphome itself. It only affects the way the docket init script instantiate esphome. I can totally rename if you have a better idea

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