Add thermostat docs (#7110)

source/_lovelace/thermostat.markdown

@@ -0,0 +1,36 @@
+---
+layout: page
+title: "Thermostat Card"
+sidebar_label: Thermostat
+description: "The thermostat card allows you to control a climate entity."
+date: 2018-10-25 10:28 +00:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+---
+
+The thermostat card gives control of your climate entity.
+
+<p class='img'>
+  <img src='/images/lovelace/lovelace_thermostat_card.gif' alt='Screenshot of the thermostat card'>
+  Screenshot of the thermostat card.
+</p>
+
+{% configuration %}
+type:
+  required: true
+  description: thermostat
+  type: string
+entity:
+  required: true
+  description: Entity id of `climate` domain
+  type: string
+{% endconfiguration %}
+
+## {% linkable_title Example %}
+
+```yaml
+- type: sensor
+  entity: climate.nest
+```