Rename preset.js to preset.cjs

[unional]

This repo is esm (type: module), so the .js extension is treated as esm, not cjs.

this causes the storybook build failure in 9.1.10

[igrlk]

Hey @unional. I tested the addon with 9.1.16 and couldn't reproduce the issue. Can you upgrade to storybook@9.1.16 and see if it solves the problem?

I also just shipped a new version of the addon storybook-addon-test-codegen@3.0.0 which is compatible with storybook@10.

[unional]

If you test is within the repo, you won't able to repro it as Vite uses rollup for local code and esbuild on dependencies.

I also need to update my addons to support v10 but that will take a while.
It would be great if you can address this in v2 so that it will work on Storybook v9.

In this PR, I change the filename as that's the easier way to fix the issue.
As Storybook v10 is ESM only, you can also change the content to ESM instead. But since you already release v3, you can probably keep this and release it in a v2 branch.

[igrlk]

I initialized a new react-vite project with storybook@9.1.16 outside of this repo, and everything worked fine. Please add a minimal reproducible repo, this way I can:

1. Reproduce the error that I couldn't get locally on a brand new project
2. Apply your fix and verify it fixes the problem without causing any side effects