Expose zmq_z85_encode and zmq_z85_decode

[sirudog]

Hi,

I would like to use the Z85 encoding (https://rfc.zeromq.org/spec:32/Z85/) in my project and I was wondering how much effort would it be to expose these functions. I see that a related function (zmq_curve_keypair) is already exposed, which internally uses Z85 encoding. I am willing to help, but I am completely new to node-gyp, and I do not have much c++ knowledge. It seems to me that it is an easy win and not a lot of work, but I may miss something and I have limited time to spend on this, so any guidance is more than welcome. Thanks in advance

[reqshark]

you should check out some of @msealand's stuff on this and #414 has some background on the curvekeypair function

[sirudog]

Thanks @reqshark I'll take a look at it