Update escape-string-regexp

Author: wooorm

package.json

@@ -27,7 +27,7 @@
     "index.js"
   ],
   "dependencies": {
-    "escape-string-regexp": "^2.0.0",
+    "escape-string-regexp": "^4.0.0",
     "hast-util-is-element": "^1.0.0",
     "unist-util-visit-parents": "^3.0.0"
   },