Allow to add groups 😉

[erkr]

Similar to auto entities, populate the graphs of the card with a group (i.e temp sensors). Last line in the example:

graphs:
  - type: line
    title: Temperature 
    entities:
      - entity: sensor.forecast
      - group: sensor.outdoor_temps

A valid 'group entity' is every entity that hosts an attribute entity_id containing a list of entities. Example (Dev Tools):

state_class: measurement
entity_id:
  - sensor.lumi_lumi_weather_85afe307_temperature
  - sensor.lumi_lumi_weather_d504e207_temperature
  - sensor.lumi_lumi_weather_8199e406_temperature
  - sensor.tz2000_a476raq2_ts0201_a0e5c2fe_temperature
unit_of_measurement: °C
device_class: temperature
icon: mdi:thermometer
friendly_name: Temperatures outdoor