Add support for ZFSBootMenu

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Is your feature request related to a problem? Please describe.
ZFS-on-root systems are generally bootable from ZFSBootMenu. This EFI image includes many useful utilities (especially the Recovery variant).

Describe the solution you'd like
Could you please consider the addition of the Recovery image (auto-redirecting URL to latest release) of ZFSBootMenu to netboot.xyz? (The regular image is a strict subset of the Recovery image, so the Recovery is an all-in-one.)

Describe alternatives you've considered
There is no exact alternative.