chore(package): update react-dom to version 16.8.4

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "lint-staged": "^8.1.4",
     "prettier": "^1.16.4",
     "react": "16.8.4",
-    "react-dom": "16.8.3",
+    "react-dom": "16.8.4",
     "react-test-renderer": "16.8.3",
     "rxjs": "^6.4.0",
     "sinon": "^7.2.4",