Storysource: Fix import error

[unional]

This PR fixes a specific case of #23972 for @storybook/addon-storysource.

What I did

This works for storysource as the underlying ./dist/preset.js is still in CJS.

In general, there are a few issues:

• the addons didn't have type: module in their package.json.
• The consumer (vite or webpack I assume) are reading them as CJS as a result thus the error.
• The {addon}/manager.js and {addon}/preview.js are meant for CJS consumption (as ESM will use the info in the exports field in the package.json). So they should be in CJS format. However, that means the code they reference should also in CJS which most of them are not (except for storysource's preset).

That means a better fix is adding the type: module and removing the {addon}/manager.js and {addon}/preview.js files.

I can create another PR for that (which needs more testing).

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

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

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
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  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
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core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>