Add guided installation option for LUKS/dm-crypt full-disk encryption

[MarkusZoppelt]

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Please add an option to the installer to perform a full-disk encryption setup, e.g. according to https://docs.voidlinux.org/installation/guides/fde.html

For reference, arch has a similar option with archinstall

[MarkusZoppelt]

just noticed that there is PR #161

Can be closed as soon as it is merged.