add gm for-each to sugar extra

[amtoine]

as can be seen in the CI, we have an issue because gm for-each is trying to use gm status and gm list which come from another module, namely nu-git-manager 👀

reproduce with either

nu -n -c "
    use ./src/nu-git-manager-sugar extra 'gm for-each';
    gm for-each {}
"

or

use toolkit.nu
toolkit test