add docs for Channels media player (#4842)

* add docs for Channels media player

* note about favorite channels

* Minor cleanup

source/_components/media_player.channels.markdown

@@ -0,0 +1,61 @@
+---
+layout: page
+title: "Channels"
+description: "Instructions on how to integrate Channels into Home Assistant."
+date: 2018-03-06 11:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: channels.png
+ha_category: Media Player
+ha_release: 0.65.0
+ha_iot_class: "Local Polling"
+---
+
+
+The Channels platform allows you to control [Channels](https://getchannels.com/) from Home Assistant. Play, pause, seek, or skip commercials on an instance of Channels that is running on your network.
+
+Your favorite channels will appear as sources in the Source List in Home Assistant.
+
+To add Channels to your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+media_player:
+  - platform: channels
+    name: Family Room Channels
+    host: 192.168.1.50
+```
+
+Configuration variables:
+
+- **host** (*Required*): The IP of the device running Channels, e.g., 192.168.1.50
+- **port** (*Optional*): The port where Channels is accessible, defaults to 57000.
+- **name** (*Optional*): The name of the Channels instance in Home Assistant, eg. Family Room Channels. Defaults to Channels.
+
+### {% linkable_title Service `channels_seek_forward` %}
+
+Seek forward by the number of seconds currently set in settings on the instance of Channels.
+
+| Service data attribute | Optional | Description |
+| ---------------------- | -------- | ----------- |
+| `entity_id` | no | String that points at `entity_id` of Channels app.
+
+
+### {% linkable_title Service `channels_seek_backward` %}
+
+Seek backward by the number of seconds currently set in settings on the instance of Channels.
+
+| Service data attribute | Optional | Description |
+| ---------------------- | -------- | ----------- |
+| `entity_id` | no | String that points at `entity_id` of Channels app.
+
+### {% linkable_title Service `channels_seek_by` %}
+
+Seek forward or backward by a provided number of seconds.
+
+| Service data attribute | Optional | Description |
+| ---------------------- | -------- | ----------- |
+| `entity_id` | no | String that points at `entity_id` of Channels app.
+| `seconds` | no | Number of seconds to seek in the timeline by. Negative seconds seeks backwards.