Add preview releases

[HiDeoo]

Description

As discussed, this PR adds support for preview releases in the monorepo using pkg.pr.new.

The worflow is heavily inspired by the one used in the Astro repo with the following changes:

• Maintainers can trigger a preview release by adding the pr-preview label (it's not possible to trigger it directly using a comment).
• A little bit stricter permissions (I don't think we need write access to the issues and id-token scope).
• I added some comments to the step computing the packages to be included as it was not really obvious to me at first glance to understand exactly what was going on and I needed to run it locally to verify the output.
• I also added a bit more logic to this step to compute the list of package paths as needed by the pkg-pr-new command rather than doing it later so all logic is in one place.
• If no packages are published, the workflow errors out with a message indicating to make sure there are changesets included in the PR. I think I would prefer to see an error than waiting for the comment to show up before realizing the action succeeded but nothing was published.

Also checked the workflow using zizmor, and only an info for prefer trusted publishing for authentication is reported for pnpm dlx pkg-pr-new publish but this sounds like a false positive for pnpm publish as there is no trusted publishing possible here afaik.

If I'm not mistaken, I think we need this PR to be merged first before being able to test the entire process though so probably need a thorough review before merging in case I made any mistake.

Note that when we would want to use preview releases with #3572, we would also need to edit this workflow to include a build step.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 2651cee

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[netlify]

✅ Deploy Preview for astro-starlight ready!

Name	Link
🔨 Latest commit	2651cee
🔍 Latest deploy log	https://app.netlify.com/projects/astro-starlight/deploys/69330e8167ffe3000777abed
😎 Deploy Preview	https://deploy-preview-3610--astro-starlight.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 100 (🟢 up 14 from production) Accessibility: 100 (no change from production) Best Practices: 100 (no change from production) SEO: 100 (no change from production) PWA: - View the detailed breakdown and full score reports

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[delucis]

Thanks @HiDeoo — this will be fun to have and super helpful for sure.

Left a few questions just to make sure I understand everything!

[trueberryless]

Very interested to see this in action, I left some of my thoughts. Wonderful implementation so far, couldn't spot a single mistake 🙌

[delucis]

Let’s see how this breaks!

Just kidding — I believe in you (but not in GitHub Actions…)