domain expiry (#5242)

* domain expiry

* config

* config

source/_components/sensor.domain_expiry.markdown

@@ -0,0 +1,37 @@
+---
+layout: page
+title: "Domain Expiry"
+description: "Instructions on how to set up Domain expiry sensors within Home Assistant."
+date: 2018-04-24 14:14
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: home-assistant.png
+ha_category: System Monitor
+ha_release: 0.69
+ha_iot_class: "depends"
+---
+
+The `domain_expiry` sensor gets whois information about domain and displays the expiry in days. 
+
+To add the Domain Expiry sensor to your installation, add these options to `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: domain_expiry
+    domain: home-assistant.io
+```
+
+{% configuration %}
+domain:
+  description:  Domain name to track
+  required: true
+  type: string
+name: 
+  description: The friendly name for the certificate.
+  required: false
+  type: string
+  default: Domain Expiry
+{% endconfiguration %}