Fixed missing export of card-markdown card

no issue
- fixes the bug introduced in 0833b28557

core/server/lib/mobiledoc/cards/card-markdown.js

@@ -1,4 +1,7 @@
+'use strict';
+
 // this card is just an alias of the `markdown` card which is necessary because
 // our markdown-only editor was using the `card-markdown` card name
-let markdownCard = require('./markdown');
-module.exports = markdownCard;
+const markdownCard = require('./markdown');
+
+module.exports = Object.assign(markdownCard, {name: 'card-markdown'});

core/server/lib/mobiledoc/cards/index.js

@@ -1,6 +1,7 @@
 var hr = require('./hr'),
     html = require('./html'),
     image = require('./image'),
-    markdown = require('./markdown');
+    markdown = require('./markdown'),
+    cardMarkdown = require('./card-markdown');
 
-module.exports = [hr, html, image, markdown];
+module.exports = [hr, html, image, markdown, cardMarkdown];