make the information on the area card configurable

[ChristophCaina]

Hi there,

there are several tickets already open (and some have been closed by setting an entity to hidden) for the area cards, which have the topic that the summary of certain entities seems to be wrong.

Examples:
#21049
#20687
#20014
#19837

#20749

and probably some more...

I really like the approach of having those information visible in the area card, but I would like to consider another approach to this - similar, as it is the case for the picture-entity card.

It would be great, if you could just add one - or multiple sensors (specific to the already supported classes) to the card - and select, if they should average, or sum together.
If only one entity would be configured, then it will show the value of this specific entity.

This should also be possible for the lights and switches that will be shown on that card...

It would allow a much more flexible configuration, especially, if you add new devices to the area - and not always think about to change a new entity to "hidden" just for your area card...