Some service-row fields are now optional (#7201)

* service-data now optional

https://github.com/home-assistant/home-assistant-polymer/pull/1894

* additional fields made optional

`icon` and `action_name` will be optional as well

* 🚑 Fixes build

source/_lovelace/entities.markdown

@@ -72,20 +72,22 @@ name:
   required: true
   description: Main Label.
   type: string
-icon:
-  required: true
-  description: "Icon to display (e.g., `mdi:home`)"
-  type: string
-action_name:
-  required: true
-  description: Button label.
-  type: string
 service:
   required: true
   description: "Service like `media_player.media_play_pause`"
   type: string
+icon:
+  required: false
+  description: "Icon to display (e.g., `mdi:home`)"
+  type: string
+  default: "`mdi:remote`"
+action_name:
+  required: false
+  description: Button label.
+  type: string
+  default: "`Run`"
 service_data:
-  required: true
+  required: false
   description: The service data to use.
   type: object
 {% endconfiguration %}