fix: add missing newSplitChunks in schema.js

[hyf0]

Related issue (if exists)

Summary

🤖 Generated by Copilot at 5a8bea2

This pull request enhances the webpack configuration schema for rspack by adding SplitChunksPlugin support and fixing TypeScript errors. It affects the optimization and externals options in schema.js.

Walkthrough

🤖 Generated by Copilot at 5a8bea2

• Add a new option newSplitChunks to enable the new SplitChunksPlugin for chunk splitting (link)
• Remove the tsType property from the function option of the externals schema to fix TypeScript errors (link)

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Latest commit: 5a8bea2

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