Add support for Airthing Wave Mini

[ncareau]

What does this implement/fix?

Add support for the Airthing Wave Mini BLE device.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#1505

Test Environment

• ESP32
• ESP8266

Example entry for config.yaml:

Sensors:

  - platform: airthings_wave_mini
    ble_client_id: airthingsmini
    update_interval: 5min # default
    temperature:
      name: "WaveMini Temperature"
    humidity:
      name: "WaveMini Humidity"
    pressure:
      name: "WaveMini Pressure"
    tvoc:
      name: "WaveMini VOC"   

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @ncareau,
Thanks for submitting this pull request! Can you add yourself as a codeowner for this integration? This way we can notify you if a bug report for this integration is reported.
In __init__.py of the integration, please add:

CODEOWNERS = ["@ncareau"]

And run script/build_codeowners.py

_{^{(message by NeedsCodeownersLabel)}}

[ncareau]

Hello, I've made this PR in particular for the event hacktoberfest by digital ocean : https://hacktoberfest.digitalocean.com. I would really appreciate if you could add the label hacktoberfest-accepted to this PR (or add a label hacktoberfest to the project) in order to make my PR count towards my goal. Thank you.

[jesserockz]

Hello, I've made this PR in particular for the event hacktoberfest by digital ocean : hacktoberfest.digitalocean.com. I would really appreciate if you could add the label hacktoberfest-accepted to this PR (or add a label hacktoberfest to the project) in order to make my PR count towards my goal. Thank you.

ESPHome is already participating, and PRs will count once approved or merged =)
No need for extra labels

[jesserockz]

LGTM

[ncareau]

Thanks a lot.