nongnu: Add bluetuith.

Bluetuith is a TUI-based Bluetooth connection manager, which can interact with Bluetooth adapters and devices. It is free and open source and could probably be built from sources, but even the developer gave up due to how involved packaging Go can be for Guix (see https://github.com/darkhz/bluetuith/issues/7).

I certainly do not have the skills to do it better myself, even if the Go importer is efficient. The developer has been very helpful but the objective to source-build has kind of stalled since more than a year now, for the above reasons, so I feel a nonguix package could still be welcome and useful to others. That is fine if the MR is deemed unnecessary and if a source-based package for Guix is preferred, but I don't think I could write and maintain it with my current knowledge of Scheme.