Onyx provides access to the Gopher protocol to the OverbiteNX extension
for Firefox.  It is necessary to circumvent the fact that Firefox's
WebExtensions framework does not provide TCP/IP access to extensions.

You need to have Firefox (version 60 or above) with the OverbiteNX
extension installed to be able to make use of this package.  It will
build without either, but it will be useless.
