chore: add tests for directory redirects for gateways

[achingbrain]

Adds tests to ensure gateway and subdomain gateways return redirects that are browser-cacheable.

Refs: https://github.com/ipfs-shipyard/helia-service-worker-gateway/issues/62#issuecomment-1981379184

Change checklist

• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation if necessary (this includes comments as well)
• [x] I have added tests that prove my fix is effective or that my feature works

[github-actions[bot]]

:tada: This PR is included in version 1.1.1 :tada:

The release is available on npm package (@latest dist-tag)

Your semantic-release bot :package::rocket:

[github-actions[bot]]

:tada: This PR is included in version 1.4.0 :tada:

The release is available on npm package (@latest dist-tag)

Your semantic-release bot :package::rocket:

[github-actions[bot]]

:tada: This PR is included in version 1.0.0 :tada:

The release is available on npm package (@latest dist-tag)

Your semantic-release bot :package::rocket:

[github-actions[bot]]

:tada: This PR is included in version 1.0.0 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: