docs: Add airthings wave plus docs (#1081)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

components/sensor/airthings_ble.rst

@@ -0,0 +1,79 @@
+AirThings BLE Sensors
+========================
+
+.. seo::
+    :description: Instructions for setting up AirThings bluetooth-based sensors in ESPHome.
+    :keywords: AirThings, BLE, Bluetooth, Wave Plus
+
+The ``airthings_wave_plus`` sensor platform lets you track the output of AirThings Bluetooth Low Energy devices.
+
+This component will track radon, airborne chemicals, CO2, temperature and humidity and others depending on the device sensors.
+
+Device Discovery
+-----------------
+
+AirThings devices can be found using the ``airthings_ble`` ble scanner.
+
+To find out your device's MAC address, add the following to your ESPHome configuration:
+
+.. code-block:: yaml
+
+    logger:
+      level: DEBUG # Required for the tracker to show the device
+
+    esp32_ble_tracker:
+    airthings_ble:
+
+The device will then listen for nearby devices, and display a message like this one:
+
+``
+[D][airthings_ble:019]: 
+Found AirThings device Serial: 123456789 (MAC: 01:02:03:04:05:06)
+``
+
+Once the device is found, **remove the ``airthings_ble:`` device tracker** from your configuration and take note of the device MAC address, and use it when configuring a sensor below.
+
+Supported Devices
+-----------------
+
+Wave Plus
+*********
+
+AirThings Wave Plus tracks radon (24h and long term), airborne chemicals, CO2, temperature, atmospheric pressure and humidity.
+
+.. figure:: images/airthings_wave_plus.jpg
+    :align: center
+    :width: 60.0%
+
+Configuration example:
+
+.. code-block:: yaml
+
+    sensor:
+      - platform: airthings_wave_plus
+        ble_client_id: airthings01
+        update_interval: 5min # default
+        temperature:
+          name: "WavePlus Temperature"
+        radon:
+          name: "WavePlus Radon"
+        radon_long_term:
+          name: "WavePlus Radon Long Term"
+        pressure:
+          name: "WavePlus Pressure"
+        humidity:
+          name: "WavePlus Humidity"
+        co2:
+          name: "WavePlus CO2"
+        tvoc:
+          name: "WavePlus VOC"
+
+    ble_client:
+      - mac_address: 01:02:03:04:05:06
+        id: airthings01
+
+    esp32_ble_tracker:
+
+.. note::
+
+    The sensor uses active polling of devices every 5 minutes as per the device reported internal refresh timeout.

index.rst

@@ -163,6 +163,7 @@ Air Quality
 ***********
 .. imgtable::
 
+    AirThings BLE, components/sensor/airthings_ble, airthings_logo.png, Radon, CO2, Volatile organics
     CCS811, components/sensor/ccs811, ccs811.jpg, CO2 & Volatile organics
     HM3301, components/sensor/hm3301, hm3301.jpg, Particulate
     MH-Z19, components/sensor/mhz19, mhz19.jpg, CO2 & Temperature
@@ -250,6 +251,7 @@ Environmental
 .. imgtable::
 
     AHT10, components/sensor/aht10, aht10.jpg, Temperature & Humidity
+    AirThings BLE, components/sensor/airthings_ble, airthings_logo.png, Temperature & Humidity & Pressure
     AM2320, components/sensor/am2320, am2320.jpg, Temperature & Humidity
     BME280, components/sensor/bme280, bme280.jpg, Temperature & Humidity & Pressure
     BME680, components/sensor/bme680, bme680.jpg, Temperature & Humidity & Pressure & Gas