Update through2 to the latest version 🚀 (#124)

## The dependency [through2](https://github.com/rvagg/through2) was updated from `2.0.5` to `3.0.0`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

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[Find out more about this release](https://github.com/rvagg/through2).

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package-lock.json

@@ -23,7 +23,7 @@
     "mkdirp": "^0.5.0",
     "multimatch": "^2.0.0",
     "rimraf": "^2.2.8",
-    "through2": "^2.0.0",
+    "through2": "^3.0.0",
     "vinyl": "^2.0.1"
   },
   "devDependencies": {