Update stringify-entities

See: <https://github.com/wooorm/stringify-entities/releases/tag/2.0.0>.

Author: wooorm

package.json

@@ -26,7 +26,7 @@
     "html-void-elements": "^1.0.0",
     "property-information": "^5.0.0",
     "space-separated-tokens": "^1.0.0",
-    "stringify-entities": "^1.0.1",
+    "stringify-entities": "^2.0.0",
     "unist-util-is": "^2.0.0",
     "xtend": "^4.0.1"
   },