refactor!: ship ESM-only builds

[joshuaellis]

Summary

react-spring now ships ESM only. Every package emits a single modern ESM bundle (dist/<name>.modern.mjs) and its .d.mts types, replacing the previous dual CJS/ESM output.

Breaking changes

• ESM consumers are unaffected — Vite, webpack 5, Next, esbuild, Bun, Deno, and native Node ESM already resolved modern.mjs.
• CommonJS consumers must migrate to ESM, or run on Node ≥22.12 where require() of an ESM package is supported via interop.
• Webpack 4 is no longer supported.

[changeset-bot]

🦋 Changeset detected

Latest commit: 97f5f79

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

Name	Type
@react-spring/web	Major
@react-spring/parallax	Major
@react-spring/animated	Major
@react-spring/core	Major
@react-spring/mock-raf	Major
@react-spring/rafz	Major
@react-spring/shared	Major
@react-spring/types	Major
@react-spring/three	Major

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