Bump mem, react-native-fs and react-native-windows in /Example

Bumps [mem](https://github.com/sindresorhus/mem) to 5.1.1 and updates ancestor dependencies [mem](https://github.com/sindresorhus/mem), [react-native-fs](https://github.com/itinance/react-native-fs) and [react-native-windows](https://github.com/microsoft/react-native-windows/tree/HEAD/vnext). These dependencies need to be updated together.


Updates `mem` from 1.1.0 to 5.1.1
- [Release notes](https://github.com/sindresorhus/mem/releases)
- [Commits](sindresorhus/memoize@v1.1.0...v5.1.1)

Updates `react-native-fs` from 2.16.6 to 2.20.0
- [Release notes](https://github.com/itinance/react-native-fs/releases)
- [Changelog](https://github.com/itinance/react-native-fs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/itinance/react-native-fs/commits/v2.20.0)

Updates `react-native-windows` from 0.57.2 to 0.71.0
- [Release notes](https://github.com/microsoft/react-native-windows/releases)
- [Changelog](https://github.com/microsoft/react-native-windows/blob/react-native-windows_v0.71.0/vnext/CHANGELOG.md)
- [Commits](https://github.com/microsoft/react-native-windows/commits/react-native-windows_v0.71.0/vnext)

---
updated-dependencies:
- dependency-name: mem
  dependency-type: indirect
- dependency-name: react-native-fs
  dependency-type: direct:production
- dependency-name: react-native-windows
  dependency-type: indirect
...

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Author: dependabot[bot]