Have only integration provide multiple sensors

[foosel]

As also mentioned in #1 and the README it would be nice to have this integration to allow for selection of multiple counties during setup and then just have one integration instance provide multiple sensors.

My problem is that I'm currently unclear on how to realize this with the configuration flow, I could so far only locate examples that gather one option from a list to choose from, not multiple.

Any help on how to achieve this is greatly appreciated.