feat(legacy): export Options

[IlyaSemenov]

Description

This makes @vitejs/plugin-legacy export its Options interface. Closes #14931.

Additional context

Should the need for the type export be documented in the code? Not sure what's the policy.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines, especially the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Update the corresponding documentation if needed.
• Ideally, include relevant tests that fail without this PR but pass with it.

[sapphi-red]

LGTM

Should the need for the type export be documented in the code?

I think it's fine without it. 👍
To me, the reason for this feels obvious.

[bluwy]

FYI you can also access the options today with Parameters<typeof legacyPlugin>[0]

[IlyaSemenov]

@bluwy Thanks for the heads up. I have already elaborated on accessing the options in #14931. Yes, I can access the type, but users of my library can't. The type derived with Parameters<typeof ..> can't be re-exported.