Add guile binding at share/guile/site/libfive.scm

[KoviRobi]

Something like this seems to work, now I can do

(use-modules (libfive)
             (libfive kernel)
             (libfive vec)
             (libfive csg)
             (libfive shapes))

Fixes #336

[KoviRobi]

Currently trying to figure out how to compile the three components separately (libfive, libfive-guile, libfive-studio), which would make the licenses less ambiguous at least. That might be a different PR though.

[KoviRobi]

Also, I wonder if we could perhaps just have a minimal (libfive) module that does the C api, and ship the rest of the files a both .scm and .go files, that might be better (e.g. better editor support -- looking up source-code, etc)

[mkeeter]

I ended up moving all the bindings to Scheme (using the C FFI for everything) in #383, so I'll close this PR.