Revert "feat: remove previews (#491)"

[nickfloyd]

This reverts commit cb0835b.

This reverts #491 because removing the previews logic broke the build for our enterprise modules such as plugin-enterprise-server.js, because of old versions of GHE such as v3.2 and v3.3 (set to be deprecated next week).

Also, because GraaphQL previews are not deprecated yet @octokit/core, @octokit/graphql, and octokit.js will need to be modified.

I missed these things in my review, which is why I am reverting this changeset; so that we can modify the other libraries first and then remove this logic.

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Behavior

Before the change?

• Previews logic was removed

After the change?

• Previews logic has been reintroduced.

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Additional info

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Added the appropriate label for the given change

Does this introduce a breaking change?

• Yes (Please add the Type: Breaking change label)
• No

If Yes, what's the impact:

• N/A

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[octokitbot]

🎉 This PR is included in version 8.1.1 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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