Luftdaten: Add Support for Statistics Graph

[sethiele]

The problem

With Release 2021.8.0 the Statistics Graph was added. To use the "Luftdaten" sensor values as source for the Statistics Graph the values should set the state_class to measurement Details: https://developers.home-assistant.io/docs/core/entity/sensor/#long-term-statistics

What is version of Home Assistant Core has the issue?

core-2021.8.6

What was the last working version of Home Assistant Core?

core-2021.8.6

What type of installation are you running?

Home Assistant Supervised

Integration causing the issue

Luftdaten

Link to integration documentation on our website

https://www.home-assistant.io/integrations/luftdaten/

Example YAML snippet

No response

Anything in the logs that might be useful for us?

Sensor Data:

attribution: Data provided by luftdaten.info
sensor_id: 1xxx
longitude: 13.xxx
latitude: 52.xxx
unit_of_measurement: µg/m³
icon: mdi:thought-bubble

### Additional information

_No response_

[probot-home-assistant[bot]]

Hey there @fabaff, mind taking a look at this issue as it has been labeled with an integration (luftdaten) you are listed as a code owner for? Thanks! _{^{(message by CodeOwnersMention)}}

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