Why is PagerControl always in preview and not officially in WinUI 2 and WinUI 3

[Gaoyifei1011]

Why is PagerControl always in preview and not officially in WinUI 2 and WinUI 3

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为什么 PagerControl 一直处于预览版，没有正式进入到 WinUI 2 和 WinUI 3

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In the PagerControl implementation code, idl files still retain the MUX_PREVIEW tag instead of the MUX_PUBLIC tag

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在 PagerControl 的实现代码中，idl 文件至今仍然保留着 MUX_PREVIEW 标签，而不是 MUX_PUBLIC 标签

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#268