chore(deps): update dependency file-loader to v4 (#416)

Author: renovate[bot]

package-lock.json

@@ -54,7 +54,7 @@
     "eslint-plugin-import": "^2.18.2",
     "eslint-plugin-prettier": "^3.1.0",
     "express": "^4.17.1",
-    "file-loader": "^3.0.1",
+    "file-loader": "^4.2.0",
     "husky": "^3.0.1",
     "jest": "^24.9.0",
     "jest-junit": "^7.0.0",