fix: mark @babel/core as optional peer dependency

[spa5k]

Fixes The missing dependency error that comes while installing it through Yarn 2, Yarn 3.
and also fixes #736

Error -
styled-jsx@npm:4.0.0 [78a22] doesn't provide @babel/core (pad17e), requested by @babel/plugin-syntax-jsx

The user needs to add

packageExtensions:
  styled-jsx@*:
    dependencies:
      "@babel/core": "*"

in .yarnrc.yml even when they're not using this dependency directly, for example while using next.js

[huozhi]

This jsx plugin should use @babel/core on user side so we don't want it to become dependency.

We can add the meta field to package.json to declare it as optional

"peerDependenciesMeta": {
  "@babel/core": {
    "optional": true
  }
}

[spa5k]

Thanks for the info, did not knew this option existed.

[huozhi]

Thanks!

[github-actions]

🎉 This PR is included in version 4.0.1 🎉

The release is available on:

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

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