Add docs for 17track.net sensor platform (#7303)

* Add docs for 17track.net sensor platform

* Addressing feedback

* ⬆️ ha_release

source/_components/sensor.17track.markdown

@@ -0,0 +1,52 @@
+---
+layout: page
+title: "17track.net"
+description: "Instructions on how to use 17track.net data within Home Assistant"
+date: 2018-10-31 10:42
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: 17track.jpg
+ha_category: Postal Service
+ha_release: 0.83
+ha_iot_class: "Cloud Polling"
+---
+
+The 17track.net sensor platform allows users to get package data tied to their
+17track.net account. The platform creates both summary sensors, which show the
+number of packages in a current state (e.g., "In Transit"), as well as
+individual sensors for each package within the account.
+
+## {% linkable_title Configuration %}
+
+To enable the platform, add the following lines to your `configuration.yaml`
+file:
+
+```yaml
+sensor:
+  - platform: seventeentrack
+    username: <EMAIL ADDRESS>
+    password: <PASSWORD>
+```
+
+{% configuration %}
+username:
+  description: The email address associated with your 17track.net account.
+  required: true
+  type: string
+password:
+  description: The password associated with your 17track.net account.
+  required: true
+  type: string
+show_archived:
+  description: Whether sensors should be created for archived packages.
+  required: false
+  type: boolean
+  default: false
+show_delivered:
+  description: Whether sensors should be created for delivered packages.
+  required: false
+  type: boolean
+  default: false
+{% endconfiguration %}