Bump react-dom from 16.11.0 to 16.12.0 (#3919)

Bumps [react-dom](https://github.com/facebook/react/tree/HEAD/packages/react-dom) from 16.11.0 to 16.12.0.
- [Release notes](https://github.com/facebook/react/releases)
- [Changelog](https://github.com/facebook/react/blob/master/CHANGELOG.md)
- [Commits](https://github.com/facebook/react/commits/v16.12.0/packages/react-dom)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -60,7 +60,7 @@
     "postcss-cli": "^6.1.3",
     "prop-types": "^15.7.2",
     "react": "^16.12.0",
-    "react-dom": "^16.11.0",
+    "react-dom": "^16.12.0",
     "react-ga": "2.7.0",
     "shx": "^0.3.2",
     "webpack": "^4.41.2",