feat!: migrate to esm, upgrade `execa` to v8, tsup to v8

[beeequeue]

BREAKING CHANGE: Migrated package to ESM

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• Upgraded execa to v8
• Migrated the package to ESM
• Upgraded tsup to v8

Since execa is now a ESM package this package also needs to migrate to it.

The main reason for not upgrading fully to v9 is that it drops support for node <18.19 which we may want to keep supporting. If we don't, I can do that upgrade as well.

This will be a breaking change for the programmatic API, while the normal CLI should work just like before.

Not sure whether to mark the PR as feat or chore

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The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
tsup	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 19, 2024 11:32pm

[socket-security[bot]]

New and removed dependencies detected. Learn more about Socket for GitHub ↗︎

Package	New capabilities	Transitives	Size	Publisher
npm/execa@8.0.1	environment Transitive: filesystem, shell	+16	301 kB	ehmicky
npm/tsup@8.0.2	environment, eval, filesystem Transitive: shell	+16	710 kB	egoist

🚮 Removed packages: npm/cac@6.7.12, npm/debug@4.3.2, npm/tsup@7.1.0

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