Add the packaging metadata to build the base58 snap

[come-maiz]

This package will let you publish the latest base58 in the Ubuntu store, and from there reach many users on all the supported Ubuntu versions, and Linux distributions. You just have to go to https://build.snapcraft.io and enable the automated continuous delivery.

[keis]

I don't know much about snaps but from a quick perusal of the docs it looks to be mainly for GUI applications, e.g the main way to use it is through .desktop-files. Is it all relevant for a cli tool?

Thanks for the PR either way :)

[come-maiz]

Thanks for reviewing @keis :)
This is actually more popular with command line applications at the moment, because snaps are very cool for secure servers, raspberrypi in the wild, robots and stuff like that. We are now working hard to make it shine also on GUI, so maybe that's why your results are biased that way.

Take a look for example at ipfs-cluster, parity, solidity, minio... I don't like GUIs very much, so my bias is to the other side :)

[keis]

alright cool, I'll give it a shot

[come-maiz]

Awesome! Let me know if you have any questions.