Add support for child device

[nodiaque]

Hello,

python-kasa just introduce the notion of child device for device like the KS240. It is required to be able to control each switch in a multi-device device. It would be great if it was added.

Thank you!

[flavio-fernandes]

Hi @nodiaque! You are right, I can see in the library that there is an index attribute:

Ref: https://python-kasa.readthedocs.io/en/latest/smartstrip.html

I think that can be integrated into mqtt2kasa for sure. I am currently out of cycles for doing that, but would love to play with it in the future. Thank you for creating this issue.