chore: improve demo slides source

[KermanX]

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@slidev/client

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/client@1965

create-slidev-theme

npm i https://pkg.pr.new/slidevjs/slidev/create-slidev-theme@1965

@slidev/parser

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/parser@1965

@slidev/cli

npm i https://pkg.pr.new/slidevjs/slidev/@slidev/cli@1965

create-slidev

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@slidev/types

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commit: 54fa80e

[KermanX]

I tried not to use !important here