* guix/scripts/import.scm: (importers): Add "npm-binary".
* guix/import/npm-binary.scm: New file.
* guix/scripts/import/npm-binary.scm: New file.
* Makefile.am: Add them.

Co-authored-by: Timothy Sample <samplet@ngyro.com>
Co-authored-by: Lars-Dominik Braun <lars@6xq.net>