docs: clarify content script HMR support

[Toumash]

Summary

• Update English docs to clarify that content script HMR supports both isolated world and main world.
• Update matching Chinese docs and content page descriptions.
• Link the support note to the @crxjs/vite-plugin v2.7.0 release.

Validation

• pnpm build
• git diff --check

[changeset-bot]

⚠️ No Changeset found

Latest commit: 77ac7b6

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