Freeze react-hot-loader at 4.1.2 because of hot-reload problem

From 4.1.3 up to at least 4.2.0, hot reload fails with a reference error for const `instanceId` in `WrappedLifecyclePanel` and `this.trace` definitions.

See issue gaearon/react-hot-loader#978

Author: Oblosys

package-lock.json

@@ -74,7 +74,7 @@
     "node-sass": "^4.9.0",
     "react": "^16.4.0",
     "react-dom": "^16.4.0",
-    "react-hot-loader": "^4.1.2",
+    "react-hot-loader": "4.1.2",
     "sass-loader": "^7.0.1",
     "webpack": "^4.7.0",
     "webpack-cli": "^2.1.3",