chore: update dependencies and improve README for React authentication example

[wassimoo]

• Updated @ory/client-fetch, react, and react-dom to their latest versions.
• Added a note about using the Ory Tunnel with the --dev flag for easier integration.

Related Issue or Design Document

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact security@ory.com) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

[vinckr]

Nice, thanks!

a few small formatting etc nits to resolve then can be merged imo