Add Xiaomi Cleargrass Sensor Documentation (#346)

* Add index for new Xiaomi ClearGrass E-Ink Sensor

* Add Xiaomi Cleargrass Sensor Documentation

Add all the needed documentation, such as index,
references and main page of this sensor

* Fix images width

Adjust images width to a better fit in the page

* Fix apiref of Xiaomi Sensors

The apiref of Cleargrass and LYWSD02 models point
to the mijia's api, so I fix this

* Fix Xiaomi Cleargrass documentation mistake

Line 43 of xiaomi_cleargrass.rst references to
Xiaomi Mijia's sensor. It should reference to
Xiaomi Cleargrass.

Also I change titles of this sensor in order to
avoid the title uses 2 lines

components/sensor/xiaomi_cleargrass.rst

@@ -0,0 +1,105 @@
+Xiaomi ClearGrass BLE Sensor
+============================
+
+.. seo::
+    :description: Instructions for setting up Xiaomi ClearGrass E-Ink bluetooth-based temperature and humidity sensors in ESPHome.
+    :image: xiaomi_cleargrass.jpg
+    :keywords: Xiaomi, ClearGrass, BLE, E-Ink, Bluetooth
+
+The ``xiaomi_cleargrass`` sensor platform lets you track the output of Xiaomi ClearGrass Bluetooth
+Low Energy devices using the :doc:`/components/esp32_ble_tracker`. This component will track the
+temperature, humidity and optionally the battery level of the ClearGrass device every time the
+sensor sends out a BLE broadcast. Note that contrary to other implementations, ESPHome can track as
+many ClearGrass devices at once as you want.
+
+.. figure:: images/xiaomi_cleargrass-full.jpg
+    :align: center
+    :width: 80.0%
+
+    Xiaomi ClearGrass Temperature and Humidity Sensor over BLE.
+
+.. figure:: images/xiaomi_cleargrass-ui.jpg
+    :align: center
+    :width: 80.0%
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    esp32_ble_tracker:
+
+    sensor:
+      - platform: xiaomi_cleargrass
+        mac_address: 7A:80:8E:19:36:BA
+        temperature:
+          name: "Xiaomi ClearGrass Temperature"
+        humidity:
+          name: "Xiaomi ClearGrass Humidity"
+        battery_level:
+          name: "Xiaomi ClearGrass Battery Level"
+
+Configuration variables:
+------------------------
+
+- **mac_address** (**Required**, MAC Address): The MAC address of the Xiaomi ClearGrass device.
+- **temperature** (*Optional*): The information for the temperature sensor.
+
+  - **name** (**Required**, string): The name for the temperature sensor.
+  - **id** (*Optional*, :ref:`config-id`): Set the ID of this sensor for use in lambdas.
+  - All other options from :ref:`Sensor <config-sensor>`.
+
+- **humidity** (*Optional*): The information for the humidity sensor
+
+  - **name** (**Required**, string): The name for the humidity sensor.
+  - **id** (*Optional*, :ref:`config-id`): Set the ID of this sensor for use in lambdas.
+  - All other options from :ref:`Sensor <config-sensor>`.
+
+- **battery_level** (*Optional*): The information for the battery level sensor
+
+  - **name** (**Required**, string): The name for the humidity sensor.
+  - **id** (*Optional*, :ref:`config-id`): Set the ID of this sensor for use in lambdas.
+  - All other options from :ref:`Sensor <config-sensor>`.
+
+
+Setting Up Devices
+------------------
+
+To set up Xiaomi ClearGrass devices you first need to find their MAC Address so that ESPHome can
+identify them. So first, create a simple configuration without any ``xiaomi_cleargrass`` entries
+like so:
+
+.. code-block:: yaml
+
+    esp32_ble_tracker:
+
+After uploading the ESP32 will immediately try to scan for BLE devices such as the Xiaomi
+ClearGrass. When it detects these sensors, it will automatically parse the BLE message print a
+message like this one:
+
+.. code::
+
+    Xiaomi ClearGrass 7A:80:8E:19:36:BA Got temperature=23.4°C, humidity=65.0%
+
+Note that it can sometimes take some time for the first BLE broadcast to be received. You can speed
+up the process by pressing the grey bluetooth button on the back of the device.
+
+Then just copy the address (``7A:80:8E:19:36:BA``) into a new ``sensor.xiaomi_cleargrass`` platform
+entry like in the configuration example at the top.
+
+.. note::
+
+    The ESPHome Xiaomi integration listens passively to packets the xiaomi device sends by itself.
+    ESPHome therefore has no impact on the battery life of the device.
+
+See Also
+--------
+
+- :doc:`/components/esp32_ble_tracker`
+- :doc:`/components/sensor/xiaomi_mijia`
+- :doc:`/components/sensor/xiaomi_miflora`
+- :doc:`/components/sensor/xiaomi_lywsd02`
+- :doc:`/components/sensor/index`
+- :apiref:`xiaomi_cleargrass/xiaomi_cleargrass.h`
+- `Xiaomi Mijia BLE protocol <https://github.com/mspider65/Xiaomi-Mijia-Bluetooth-Temperature-and-Humidity-Sensor>`__
+  by `@mspider65 <https://github.com/mspider65>`__
+- `OpenMQTTGateway <https://github.com/1technophile/OpenMQTTGateway>`__ by `@1technophile <https://github.com/1technophile>`__
+- :ghedit:`Edit`

components/sensor/xiaomi_lywsd02.rst

@@ -86,7 +86,7 @@ See Also
 - :doc:`/components/sensor/xiaomi_mijia`
 - :doc:`/components/sensor/xiaomi_miflora`
 - :doc:`/components/sensor/index`
-- :apiref:`xiaomi_mijia/xiaomi_mijia.h`
+- :apiref:`xiaomi_lywsd02/xiaomi_lywsd02.h`
 - `Xiaomi Mijia BLE protocol <https://github.com/mspider65/Xiaomi-Mijia-Bluetooth-Temperature-and-Humidity-Sensor>`__
   by `@mspider65 <https://github.com/mspider65>`__
 - `OpenMQTTGateway <https://github.com/1technophile/OpenMQTTGateway>`__ by `@1technophile <https://github.com/1technophile>`__

index.rst

@@ -143,6 +143,7 @@ Sensor Components
     Xiaomi MiFlora, components/sensor/xiaomi_miflora, xiaomi_miflora.jpg
     Xiaomi MiJia, components/sensor/xiaomi_mijia, xiaomi_mijia.jpg
     Xiaomi LYWSD02, components/sensor/xiaomi_lywsd02, xiaomi_lywsd02.jpg
+    Xiaomi ClearGrass, components/sensor/xiaomi_cleargrass, xiaomi_cleargrass.jpg
     ZyAura, components/sensor/zyaura, zgm053.jpg
     Custom Sensor, components/sensor/custom, language-cpp.svg