Bump linkify-it to v4

Author: Vitaly Puzrin

Diff for: package.json

@@ -39,7 +39,7 @@
   "dependencies": {
     "argparse": "^2.0.1",
     "entities": "~3.0.1",
-    "linkify-it": "markdown-it/linkify-it",
+    "linkify-it": "^4.0.0",
     "mdurl": "^1.0.1",
     "uc.micro": "^1.0.5"
   },