Add Darkmode Support

[EdisonJwa]

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Description

Add Darkmode support
Demo: https://www.wevg.org

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Verification steps

[Misaka13514]

我原来也想自己改个darkmode的
改的差不多了才发现这个pr改的比我早还改的比我好
👍 :)
darkmode颜色选取上是否需要再讨论一下？
mac这边看来的话demo要比其他darkmode的界面(如Finder/Chrome)暗了些
苏卡卡的blog要跟进下加一个favicon-dark吗ww

[EdisonJwa]

@Misaka13514 颜色选取如果有更好的提议当然好