Switch to ESM format (#47)

* Switch to ESM format

* Prettier

Author: Joel Denning

package.json

@@ -49,7 +49,7 @@
     "systemjs-webpack-interop": "^2.3.4",
     "webpack": "^5.18.0",
     "webpack-cli": "^4.4.0",
-    "webpack-config-single-spa-react": "^2.0.0",
+    "webpack-config-single-spa-react": "^5.0.2",
     "webpack-dev-server": "^4.0.0-beta.0",
     "webpack-merge": "^5.7.3"
   },