Add airco2ntrol co2 evaluation as attributes

[jansauer]

Maybe level and/or color.

Carbon dioxide levels and potential health problems are indicated below:

• 250-350 ppm: background (normal) outdoor air level
• 350-1,000 ppm: typical level found in occupied spaces with good air exchange
• 1,000-2,000 ppm: level associated with complaints of drowsiness and poor air
• 2,000-5,000 ppm: level associated with headaches, sleepiness, and stagnant, stale, stuffy air; poor concentration, loss of attention, increased heart rate and slight nausea may also be present.
• >5,000 ppm: This indicates unusual air conditions where high levels of other gases also could be present. Toxicity or oxygen deprivation could occur. This is the permissible exposure limit for daily workplace exposures.
• >40,000 ppm: This level is immediately harmful due to oxygen deprivation.

Example on how it is done:
https://github.com/home-assistant/home-assistant/blob/master/homeassistant/components/alarm_control_panel/blink.py#L67