Add Trafikverket WeatherStation documentation (#4562)

* Create sensor.trafikverket_weatherstation.markdown.markdown

* Add trafikverket.png

trafikverket.png used for trafikverket_weatherstation sensor platform.

* api_key

Updated from api to api_key due to CONF_API_KEY.

* Removed text

Removed text which I used on GitHub for the custom component. Now needed to have for the official release.

* Example picture

Added an example picture to better understand how to get the weather station.

* Added example picture

Added an example picture to better understand how to get the weather station. What the user needs to copy and add to the YAML file.

* Added usage information

Added examples of the usage (why needing the data).

* linkable_title

Changed from normal titles to linkable_title in order to follow the documentation standards.

* Updated based on feedback

Done
- Rewrote "Usage" into "Potential use cases"
- Linked to Trafikverket homepage
- Description instead of static links

* Configuration variables

Updated to use "{% configuration %}" instead of "Configuration variables" as plain text.

* HA release 0.64.0

Updated ha_release to 0.64.0 instead.

* HA release 0.65.0

Updated ha_release to 0.65.0 since it wasn't merged in 0.64.0 release.

* ✏️ Tiny improvements

* ha_release and note

Updated ha_release to 0.66.0 and removed a note about using secrets.yaml for all your API keys, usernames and passwords.

source/_components/sensor.trafikverket_weatherstation.markdown

@@ -0,0 +1,86 @@
+---
+layout: page
+title: "Trafikverket WeatherStation"
+description: "Instructions how to integrate Trafikverket WeatherStation within Home Assistant."
+date: 2018-02-01 12:06
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: trafikverket.png
+ha_category: Sensor
+ha_release: 0.66.0
+---
+
+Showing weather information for air and road temperature provided by [Trafikverket](https://www.trafikverket.se/) in Sweden. 
+
+Potential use cases:
+-	Get weather data in general
+-	You live near a weather station and want to know the current temperature at home
+-	Setup automations for your car heating system. If the road is frozen along the way to work, you might want the car heating system to start earlier.
+
+##### {% linkable_title Configuration %}
+
+To enable this sensor, add the following lines to your `configuration.yaml`.
+
+```yaml
+sensor:
+  - platform: trafikverket_weatherstations
+    name: Trafikverket Road WeatherStation Kungälv
+    api_key: eXXcbXXXacXXXXc39XX3aXXX4aXX46XX
+    station: Kungälv
+    type: road
+```
+
+{% configuration %}
+name:
+  description: Unique name of the device in the frontend.
+  required: true
+  type: string
+api_key:
+  description: API key from Trafikverket.
+  required: true
+  type: string
+station:
+  description: Name of the weather station.
+  required: true
+  type: string
+type:
+  description: Defines which temperature you want (`air` or `road`).
+  required: true
+  type: string
+scan_interval:
+  description: How frequently to query for new data (in seconds).
+  required: false
+  type: int
+  default: 300
+{% endconfiguration %}
+
+##### {% linkable_title Obtaining API key %}
+
+Please click [here](https://api.trafikinfo.trafikverket.se/) and register to obtain the API key.
+
+##### {% linkable_title Weather stations %}
+
+Click [here](https://www.trafikverket.se/trafikinformation/vag/?TrafficType=personalTraffic&map=1/606442.17/6886316.22/&Layers=RoadWeather%2b) to get a map of valid weather stations. Once a station is found, copy the name according to the below picture and paste it in your `configuration.yaml` file as the `station` variable.
+
+<p class='img'>
+  <img src='{{site_root}}/images/screenshots/get_trafikverket_weather_station_example.png' />
+</p>
+
+##### {% linkable_title Examples %}
+
+```yaml
+sensor:
+  - platform: trafikverket_weatherstations
+    name: Trafikverket Road WeatherStation Kungälv
+    api_key: eXXcbXXXacXXXXc39XX3aXXX4aXX46XX
+    station: Kungälv
+    type: road
+  - platform: trafikverket_weatherstations
+    name: Trafikverket Air WeatherStation Lanna
+    api_key: eXXcbXXXacXXXXc39XX3aXXX4aXX46XX
+    station: Lanna
+    type: air
+    scan_interval: 600
+```