Clear and concise description of the problem

Since outputOptions.footer is called for dts files, I had to write a little more code to only add code to non-dts files.
https://github.com/vitejs/vite-plugin-react/blob/ca97a985fd570260096125e67687dca63bd27eae/packages/plugin-react-swc/tsdown.config.ts#L24-L35

Suggested solution

It would be nice to have a dts boolean parameter passed to outputOptions option.

export interface Options {
  outputOptions?:
    | OutputOptions
    | ((
        options: OutputOptions,
        format: NormalizedFormat,
        dts: boolean
      ) => Awaitable<OutputOptions | void | null>)
}

Alternative

No response

Additional context

No response

Validations

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• Read the Contributing Guide.
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