[NEW] nitrocli

I am submitting a port which allows to use NitroKey hardware under
OpenBSD. It has been lightly tested on OpenBSD -current and 7.4 (amd64)
with a Nitrokey Storage 2.

Under Linux, the software responsible for accessing the NitroKey over
USB depends on udev rules to make the NitroKey available to regular
users. Since this is not an option here, we need to manually chmod+chown
the corresponding usb(4) character device. I have added a mention in the
README, but the solution seems dirty to me and I would like to hear
about alternatives, if somebody can come up with any.

nitrocli is MIT licensed, but some of the cargo modules required for
building this use licenses which are a bit more restrictive. In particular:

nitrokey-sys LGPL-3.0
nitrokey-test GPL-3.0-or-later
nitrokey-test-state GPL-3.0-or-later