[FeatureRequest] Add "rescan directory" button

[niktss]

Feature Description / 功能描述
It would be useful to have a button that rescans the directory for new unhidden files, and hides them as well.

Reason / 理由
Currently, the only way to hide files is after copying the files to the hidden directory, to then unhide all files, and then hide all again; this triggers the necessary scan to process all new files, and it takes needless time. It would be cool if we had a button that just scanned the directory for new files, without having to unhide everything first and hide it all again.

Suggest Solution / 实现方案
(Optional) Possible ways to implement this feature / （可选）如果你已想出新功能的实现方案，请在这里写出。