fix(package): point to dist instead of lib (#417)

Author: Ryan Clark

package.json

@@ -7,7 +7,7 @@
   "author": "Tobias Koppers @sokra",
   "homepage": "https://github.com/webpack-contrib/karma-webpack",
   "bugs": "https://github.com/webpack-contrib/karma-webpack/issues",
-  "main": "lib",
+  "main": "dist",
   "engines": {
     "node": ">= 8.9.0"
   },
@@ -31,7 +31,7 @@
     "defaults": "webpack-defaults"
   },
   "files": [
-    "lib"
+    "dist"
   ],
   "peerDependencies": {
     "webpack": "^4.0.0"