RFE: add sensors for Kettle state
Note that I'm a homeassistant user and have never used Homebridge before today, so apologies if my terminology is slightly off.

* **Please explain your feature request in a one or two sentences.**
I'd like to expose Kettle attributes as sensors (in homeassistant) -- primarily temperature and done-boiling/keep-warm-mode-started. The reason I installed this plugin is that I'd like to get "water done boiling" status updates into homeassistant (i.e. I don't have any use for the remote start buttons). All I really want to do is get a watch notification when my water is done. The govee app is surprisingly useless for this unless I open the app before I start the water, and I don't want to have to do that. So I'm trying to get a homeassistant notification instead.

Looks like it might be possible somewhere in the `externalUpdate()` function here: https://github.com/bwp91/homebridge-govee/blob/e0a36756b4d47c9341a77a436e644c6dbc03c5ca/lib/device/kettle.js#L220-L267  (I see temperature is commented out)

* **Any particular Govee devices that this relates to?**
7171 kettle
