fix(package): add webpack >= 4 (peerDependencies) (#101)

Author: ai

package.json

@@ -54,7 +54,7 @@
     "webpack-defaults": "^1.6.0"
   },
   "peerDependencies": {
-    "webpack": "^2.0.0 || ^3.0.0"
+    "webpack": "^2.0.0 || ^3.0.0 || ^4.0.0"
   },
   "engines": {
     "node": ">= 4.8 < 5.0.0 || >= 5.10"