change paging code to fix some bug

[mydaoyuan]

eg

1. when selection on page middle，write some world on full page , then trigger paging , selection after all paragraph will into next page.
2. when editor have two pages, i delete some world on first page, but the second page paragraph dont rise to first page

[vercel[bot]]

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[mydaoyuan]

and thanks so much to this repo 🎊 , i learn so much