Add KEF integration (#11274)

* add KEF speaker integration docs

* ✏️ Tweak

* update text for usage of aiokef v0.2.0

* ✏️ Tweak

* add port to the configuration

* update ha_release to 0.104

Co-authored-by: Franck Nijhof <frenck@frenck.nl>
Co-authored-by: Klaas Schoute <klaas_schoute@hotmail.com>

source/_integrations/kef.markdown

@@ -0,0 +1,85 @@
+---
+title: "KEF Speakers"
+description: "Instructions on how to integrate KEF Speakers into Home Assistant."
+logo: kef.png
+ha_category:
+  - Media Player
+ha_iot_class: Local Polling
+ha_release: 0.104
+---
+
+The `kef` platform allows you to control the [KEF LS50 Wireless](https://international.kef.com/products/ls50-wireless) and [KEF LSX](https://international.kef.com/products/lsx) speakers from Home Assistant.
+
+Supported devices:
+
+- KEF LS50 Wireless
+- KEF LSX (untested)
+
+To add KEF Speakers to your installation, add the following to your `configuration.yaml` file:
+
+## Configuration
+
+```yaml
+# Example configuration.yaml entry
+- platform: kef
+  host: IP_ADDRESS
+  type: LS50
+```
+
+{% configuration %}
+host:
+  description: "IP address of the device. Example: 192.168.1.32"
+  required: true
+  type: string
+type:
+  description: The speaker type, either `LS50` or `LSX`.
+  required: true
+  type: string
+name:
+  description: The name of the device
+  required: false
+  default: KEF
+  type: string
+port:
+  description: The port of the device
+  required: false
+  default: 50001
+  type: integer
+maximum_volume:
+  description: Maximum volume allowed. Number between 0 and 1.
+  required: false
+  default: 0.5
+  type: float
+volume_step:
+  description: Volume step when increasing volume.
+  required: false
+  default: 0.05
+  type: float
+inverse_speaker_mode:
+  description: Switch channels from L/R to R/L.
+  required: false
+  default: false
+  type: boolean
+standby_time:
+  description: The speakers automatically turn to standby mode after either `20` or `60` minutes. Leave out for the speaker to never go into standby mode.
+  required: false
+  type: integer
+{% endconfiguration %}
+
+## Advanced configuration example
+
+```yaml
+# Example configuration.yaml entry
+- platform: kef
+  host: IP_ADDRESS
+  type: LS50
+  name: My KEF speakers
+  maximum_volume: 0.6
+  volume_step: 0.05
+```
+
+Notes:
+
+- The LS50 Wireless is tested with the latest firmware of 19-11-2019: `p6.3001902221.105039422` and older firmware: `p6.2101809171.105039422`
+
+[KEF Speakers]: /integrations/kef/