upgrade fork-ts-checker example dependencies

Author: johnnyreilly

examples/fork-ts-checker/package.json

@@ -6,7 +6,7 @@
     "start": "webpack --watch --mode development"
   },
   "devDependencies": {
-    "fork-ts-checker-webpack-plugin": "TypeStrong/fork-ts-checker-webpack-plugin",
+    "fork-ts-checker-webpack-plugin": "^0.4.0",
     "ts-loader": "^4.0.0",
     "typescript": "^2.6.2",
     "webpack": "^4.0.0",