Add units to sensor state

[mikenorgate]

Please describe what you are trying to do with the component
I have a sensor for my 3D printer that indicates time remaining on the active print in seconds, however because only the value is passed to the LLM it's incorrectly interpreting the unit, it thinks the value represents minutes

Describe the solution you'd like
When generating the device state, if the sensor includes a unit of measurement it should be included

Additional context

[acon96]

This should be added in v0.3.3 but I'm not sure which unit to display since Home assistant seems to provide the raw units as well as preferred units and I can't figure out which one is which.