[Feature Request] Add file validation function

[DarkRRb]

I would like to be able to enter md6 sha256, etc. for automatic checksumming after the download is complete.

[monkeyWie]

What to do if the verification fails?

[DarkRRb]

Failed validation indicates that the file is corrupted and may even be dangerous, so you need to download it again!

Of course the user can also be notified and let the user decide