Fix missing dependency

Author: wooorm

package.json

@@ -31,11 +31,11 @@
     "to-markdown.js"
   ],
   "dependencies": {
-    "mdast-util-from-markdown": "^0.6.0",
+    "mdast-util-to-markdown": "^0.3.0",
     "micromark": "~2.8.0"
   },
   "devDependencies": {
-    "mdast-util-to-markdown": "^0.3.0",
+    "mdast-util-from-markdown": "^0.6.0",
     "micromark-extension-footnote": "~0.2.0",
     "nyc": "^15.0.0",
     "prettier": "^2.0.0",