Add horizon profile feature support

[thomay86]

Following up on the horizon profile implementation in the 'backend' (rany2/open-meteo-solar-forecast#23) we have to add the feature to the HA version. I guess it should be a similar kind of change like #36 ?

I'd suggest to add two new configuration fields for use_horizon (boolean) and the horizon_map. The horizon_map of course is a bit tricky; maybe as a first attempt we could provide a string type field where you can copy/paste a horizon map (e.g. from an Excel sheet) as a Python tuple of tuples? (casting "[[0,30],[360,0]]" to an actual variable? is that possible?) Or read it from some (.py?) file that has to be placed in the custom_components/open_meteo_solar_forecast directory?

I'd give it a shot, but I don't understand the workflow of integrating and testing the changed code into my HA instance (pre-installed HA Green) :-(