fix: sharding in combination with the --url cli option

[matt-halliday]

Closes #577

What I did

This adds a custom Jest sequencer if the tests are running against an index.json file (in which case test files are written to a temporary directory), and sort them by test name, rather than default which uses the path.

Checklist for Contributors

Manual testing

yarn test-storybook -u --browsers chromium --url=https://drei.pmnd.rs --shard=1/2

yarn test-storybook -u --browsers chromium --url=https://drei.pmnd.rs --shard=2/2

You will have coverage of all the components, not a random amount of them.

Documentation

• Add or update documentation reflecting your changes in this repository
• Request documentation updates in the test-runner docs website

Checklist for Maintainers

• Make sure this PR contains one of the labels below:

  Available labels

  • skip-release: Skip any releases, e.g., documentation only changes, CI config etc.
  • patch: Upgrade patch version (e.g. 0.0.x)
  • minor: Upgrade patch version (e.g. 0.x.0)
  • major: Upgrade patch version (e.g. x.0.0)

[matt-halliday]

I struggled to get this to be usable in Jest config without building it and including it in the dist folder... Not sure if there's a way to avoid that with the way jest config wants to resolve a module.

[jtbandes]

Thanks for sharing this, this fix worked perfectly for me.