Add feature to only charge during cheap hours according to PVPC

[msanchezt]

It would be super nice to add an additional feature/way of working where you can define:

• Until what % do you want to charge the battery. That is: in case the % battery charge state is available, I want to charge it until 80%, not more.
• Taking into account the PVPC hourly prices for the current/next day and the kW of your charger, only charge during "cheap hours"

I've been checking this amazing repo and I think is doable and it would be a great enhancement, to be able to charge during hours where electricity price cheap vs expensive. I see there is the "Precio MAX para cargar" option, but that does not take into account 2 elements:

• That you might need to charge it even that day electricity is expensive in general, but at least, let's use the cheapest ours.
• The % of battery of the car.