add .zst to extension list (part to solve #3990)

[wstein]

Please integrate this PR as 1st step to make the workaround for #3990 some easier.
So only command line instructions are necessary and not patching a source file.

Workaround on my installation (in addition to the patch):

scoop bucket add versions
scoop install 7zip-zstd
scoop uninstall 7zip
scoop reset 7zip-zstd

Needed to fix openssh package: ScoopInstaller/Main#1494

[wstein]

I will create a new pull request which solves #3990