Add map card documentation.

source/_lovelace/map.markdown

@@ -0,0 +1,52 @@
+---
+layout: page
+title: "Map Card"
+sidebar_label: Map
+description: "A card that allows you to display entities on a map"
+date: 2018-07-08 10:28 +00:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+---
+
+### Map
+
+A card that allows you to display entities on a map
+
+<p class='img'>
+<img src='/images/lovelace/lovelace_map_card.png' alt='Screenshot of the map card'>
+Screenshot of the map card.
+</p>
+
+**Options**
+
+| Name | Type | Default | Description
+| ---- | ---- | ------- | -----------
+| type | string | **Required** | `map`
+| entities | list | **Required** | A list of entities to display on the map. Can be entity_ids or entity objects (see structure below).
+| title | string | Optional | Card title
+| aspect_ratio | string | `"100%"` | Map height:width ratio
+
+`entity` object
+
+| Name | Type | Default | Description
+| ---- | ---- | ------- | -----------
+| entity | string | **Required** | An entity_id. Example: 'device_tracker.demo_paulus'.
+
+<p class='note'>
+  Only entities that have latitude and longitude attributes will be displayed on the map
+</p>
+
+
+**Examples**
+
+Basic map example:
+
+```yaml
+- type: map
+  aspect_ratio: 100%
+  entities:
+    - entity: device_tracker.demo_paulus
+    - group.home
+```