fix: force non-legacy import attributes babel output

[hi-ogawa]

Description

• closes [plugin:vite:esbuild] Transform failed - Importing JSON files with { type: "json" };  #385

So, what's happened is that @babel/plugin-syntax-import-attributes was necessary until quite recently, but it's now included in babel core since 7.26 https://babeljs.io/blog/2024/10/25/7.26.0#import-attributes-16579. Previously users would've seen more direct error message instead:

Add @babel/plugin-syntax-import-attributes (https://github.com/babel/babel/tree/main/packages/babel-plugin-syntax-import-attributes) to the 'plugins' section of your Babel config to enable parsing.

This monorepo had 7.25, so I actually got this error. For now, I updated @babel/core to make it work. I'll review pending renovate PR #373 since that includes @babel/core update too.

For user with version < 7.26, I assume generatorOpts.importAttributesKeyword would be no-op, so probably it's fine to always add it on our side.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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