Add Netgear LTE documentation (#5502)

* Add Netgear LTE documentation

* Address review comment

* Require default notify target

* Add missing backtick

source/_components/netgear_lte.markdown

@@ -0,0 +1,39 @@
+---
+layout: page
+title: "Netgear LTE"
+description: "Instructions on how to integrate your Netgear LTE modem within Home Assistant."
+date: 2018-06-06 23:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: netgear.jpg
+ha_release: 0.72
+ha_category: Other
+ha_iot_class: "Local Polling"
+---
+
+The Netgear LTE integration for Home Assistant allows you to observe and control [Netgear LTE modems](https://www.netgear.com/home/products/mobile-broadband/lte-modems/default.aspx), currently only tested with LB2120.
+
+The integration provides:
+* a notify service that will send an SMS
+* a sensor with the number of unread SMS messages in the inbox
+* a sensor with data usage
+
+```yaml
+# Example configuration.yaml entry
+netgear_lte:
+  - host: IP_ADDRESS
+    password: SECRET
+```
+
+{% configuration %}
+host:
+    description: The IP address of the modem web interface.
+    required: true
+    type: string
+password:
+    description: The password used for the modem web interface.
+    required: true
+    type: string
+{% endconfiguration %}

source/_components/notify.netgear_lte.markdown

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+---
+layout: page
+title: "Netgear LTE Notify"
+description: "Instructions on how to add Netgear LTE notifications to Home Assistant."
+date: 2018-06-06 23:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: netgear.png
+ha_category: Notifications
+ha_release: 0.72
+---
+
+The `netgear_lte` platform allows you to use a Netgear LTE modem for notifications from Home Assistant. The message will be sent as an SMS text message.
+
+This requires you to have set up the [Netgear LTE component](/components/netgear_lte/).
+
+```yaml
+# Example configuration.yaml entry
+notify:
+  - platform: netgear_lte
+    name: sms
+    target: "+15105550123"
+```
+
+{% configuration %}
+target:
+    description: The phone number of a default recipient or a list with multiple recipients.
+    required: true
+    type: string, list
+name:
+    description: Setting the optional parameter `name` allows multiple notifiers to be created.
+    required: false
+    default: notify
+    type: string
+host:
+    description: The modem to use. Not needed if you only have one.
+    required: false
+    type: string
+{% endconfiguration %}

source/_components/sensor.netgear_lte.markdown

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+---
+layout: page
+title: "Netgear LTE Sensor"
+description: "Instructions on how to integrate Netgear LTE sensors into Home Assistant."
+date: 2018-06-06 23:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: netgear.jpg
+ha_release: 0.72
+ha_category: Sensor
+ha_iot_class: "Local Polling"
+---
+
+The `netgear_lte` sensor platform allows you to monitor your Netgear LTE modem.
+
+This requires you to have set up the [Netgear LTE component](/components/netgear_lte/).
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: netgear_lte
+    sensors:
+      - sms
+      - usage
+```
+
+{% configuration %}
+sensors:
+    description: Sensor types to create.
+    required: true
+    type: list
+    keys:
+        sms:
+            description: Number of unread SMS messages in the modem inbox.
+        usage:
+            description: Amount of data transferred.
+host:
+    description: The modem to use. Not needed if you only have one.
+    required: false
+    type: string
+{% endconfiguration %}