Add missing dev dependency

Author: hackermd

package.json

@@ -28,6 +28,7 @@
     "rollup": "^0.63.2",
     "rollup-plugin-commonjs": "8.3.0",
     "rollup-plugin-json": "^3.0.0",
+    "rollup-plugin-node-builtins": "^2.1.2",
     "rollup-plugin-node-resolve": "^3.3.0",
     "tape": "^4.9.1"
   },