setup-disk: Add keymap to initfs if root is ZFS
Checks whether $rootfs is ZFS and adds "keymap" to $initfs_features. This is required for encrypted ZFS installations that prompt for a passphrase at boot to ensure that the appropriate keymap is used for non-US keyboard users. ref: aports#13291 (closed)
Signed-off-by: Edin Taric unicorn@regrow.earth