Option type

We require an Option type that describes an applied makepkg custom option (see https://man.archlinux.org/man/PKGBUILD.5) when a package has been built. See repod's implementation for reference: https://gitlab.archlinux.org/archlinux/repod/-/blob/cc0e43c7c858c679027068639e7db554fb78aa21/repod/common/models.py#L312-323

Although this is implemented in e.g. .BUILDINFO as a list, we actually only require the Option type.