Add support for guix packages

We should add support for https://guix.gnu.org/ packages
guix is based on nix (see https://github.com/nexB/scancode-toolkit/issues/2823 )

In contrast with nux that uses its nix language, guix is based on Guile scheme.
The doc for how packages are defined is at https://guix.gnu.org/manual/en/html_node/Defining-Packages.html
These package definitions are peculiar in that many are baked in a single scheme file like this https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/crates-io.scm#n38451 (which contains about 70K lines of scheme, and this just for the rust crates)

See https://framagit.org/upt/upt-guix/-/blob/master/upt_guix/upt_guix.py for an example for Python code that creates guix scripts.