Add docs for NMBS sensor (#7622)

* Add docs

* Update to use the standars

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Add nmbs logo

* Add note on where to find station identifiers

* Update source/_components/sensor.nmbs.markdown

Co-Authored-By: thibmaek <thibault.maekelbergh@iCloud.com>

* Change release version

* Correct key

source/_components/sensor.nmbs.markdown

@@ -0,0 +1,51 @@
+---
+layout: page
+title: "NMBS Sensor"
+description: "Instructions on how to integrate timetable data for traveling on the NMBS Belgian Railway within Home Assistant."
+date: 2018-11-24 13:47
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: sncb_nmbs.gif
+ha_category: Transport
+ha_iot_class: "Cloud Polling"
+ha_release: 0.85
+---
+
+The `nmbs` platform will create sensors for monitoring travel time and information between 2 stations.
+
+## {% linkable_title Configuration %}
+
+To enable this sensor, add the following lines to your `configuration.yaml`:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: nmbs
+    station_from: "STATION_1"
+    station_to: "STATION_2"
+    station_live: "STATION_1"
+```
+
+The stations can only be provided by their standard names and not ids. The list of stations can be checked on the NMBS/SCNB website but for most accurate results check them on the [iRail API page](https://api.irail.be/stations/) which this component uses internally.
+
+{% configuration %}
+station_from:
+  description: The station where the connection departs.
+  required: true
+  type: string
+station_to:
+  description: The station where the connection arrives.
+  required: true
+  type: string
+station_live:
+  description: Setting this will create another sensor to monitor the liveboard in a station.
+  required: false
+  type: string
+name:
+  description: Name to use in the frontend.
+  required: false
+  type: string
+  default: "`NMBS`, `NMBS Live` for the liveboard sensor when set."
+{% endconfiguration %}