Update mdast-util-to-markdown

Author: wooorm

package.json

@@ -32,7 +32,7 @@
     "to-markdown.js"
   ],
   "dependencies": {
-    "mdast-util-to-markdown": "^0.5.0",
+    "mdast-util-to-markdown": "^0.6.0",
     "parse-entities": "^2.0.0",
     "repeat-string": "^1.0.0",
     "stringify-entities": "^3.1.0",