chore(package): update react-dom to version 16.12.0

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "npm-run-all": "4.0.2",
     "nyc": "^11.1.0",
     "react": "^16.12.0",
-    "react-dom": "^16.3.0",
+    "react-dom": "^16.12.0",
     "react-router": "^3.0.4",
     "react-test-renderer": "^15.6.1",
     "sinon": "2.3.8",