Update web-components-markers.json to add maps library

Author: chrisjshull

samples/web-components-markers/web-components-markers.json

@@ -1,7 +1,7 @@
 {
     "title": "Add a Map with Markers using HTML",
     "callback": "initMap",
-    "libraries": ["marker"],
+    "libraries": ["maps", "marker"],
     "version": "beta",
     "tag": "web_components_markers",
     "name": "web-components-markers",
@@ -11,4 +11,4 @@
       "alias": "mode"
     },
     "permalink": "samples/{{ page.fileSlug }}/{{mode}}/{% if mode == 'jsfiddle' %}demo{% else %}index{% endif %}.{{ page.outputFileExtension }}"
-  }
+  }