Adding Energyforecast.de as a data source

[moritzmair]

As discussed in This issue I added a Integration for my energy price forecast site. Hope this helps to bring energy price forecasts to many users and in their smart home. For now only DE prices are supported.

This is how it looks like with Apex Charts:

[suaveolent]

Thanks, I will review it as soon as possible 👍

[suaveolent]

@moritzmair Unfortuntately the test does not work for me.

ha_epex_spot/custom_components/epex_spot/test_energyforecast.py", line 14, in main
    service = Energyforecast.Energyforecast(token=DEMO_TOKEN, session=session)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: Energyforecast.__init__() missing 1 required positional argument: 'market_area'

[moritzmair]

@suaveolent I will fix it asap

[moritzmair]

okay just fixed the test, also made the "demo_token" a working token on my side. Also added the new data source to the readme.

[suaveolent]

okay just fixed the test, also made the "demo_token" a working token on my side. Also added the new data source to the readme.

Thanks, found some minor changes. Afterwards it looks good for merge :)