chore(deps): bump webpack-dev-middleware and react-scripts in /demo

Bumps [webpack-dev-middleware](https://github.com/webpack/webpack-dev-middleware) to 5.3.4 and updates ancestor dependency [react-scripts](https://github.com/facebook/create-react-app/tree/HEAD/packages/react-scripts). These dependencies need to be updated together.


Updates `webpack-dev-middleware` from 3.7.2 to 5.3.4
- [Release notes](https://github.com/webpack/webpack-dev-middleware/releases)
- [Changelog](https://github.com/webpack/webpack-dev-middleware/blob/v5.3.4/CHANGELOG.md)
- [Commits](webpack/webpack-dev-middleware@v3.7.2...v5.3.4)

Updates `react-scripts` from 3.4.4 to 5.0.1
- [Release notes](https://github.com/facebook/create-react-app/releases)
- [Changelog](https://github.com/facebook/create-react-app/blob/main/CHANGELOG-3.x.md)
- [Commits](https://github.com/facebook/create-react-app/commits/[email protected]/packages/react-scripts)

---
updated-dependencies:
- dependency-name: webpack-dev-middleware
  dependency-type: indirect
- dependency-name: react-scripts
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>