Add documentation for the fan component

<p align="center">

  <a href="#"><img src="http://www.tooltip.gr/github_assets/smartir_fan.png" width="350" alt="SmartIR Media Player"></a>

</p>

For this platform to work, we need a .json file containing all the necessary IR or RF commands.

Find your device's brand code [here](https://github.com/smartHomeHub/SmartIR/blob/master/Docs/MEDIA_PLAYER.md#available-codes-for-fan-devices) and add the number in the `device_code` field. The compoenent will download it to the correct folder. If your device is not working, you will need to learn your own codes and place the .json file in `smartir/codes/fan/` subfolders. Please note that the `device_code` field only accepts positive numbers. The .json extension is not required.

## Configuration variables:

**name** (Optional): Name to use in the frontend<br />

**device_code** (Required): ...... (Accepts only positive numbers)<br />

**controller_send_service** (Required): The service that will be used to send the commands. Only `broadlink_send_packet` (Broadlink controller) is currently supported.<br />

**power_sensor** (Optional): *entity_id* for a sensor that monitors whether your device is actually On or Off. This may be a power monitor sensor. (Accepts only on/off states)<br />

## Example (using broadlink controller):

```yaml

smartir:

switch:

  - platform: broadlink

    host: 192.168.10.10

    mac: '00:00:00:00:00:00'

fan:

  - platform: smartir

    name: Living room fan

    device_code: 1000

    controller_send_service: switch.broadlink_send_packet_192_168_10_10

    power_sensor: binary_sensor.fan_power

```

## Available codes for Fan devices:

Below are the code files created by the people in the community. Before you start creating your own code file, try if one of them works for your device. **Please open an issue if your device is working and not included in the supported models.**