Add man page(s)

[solardiz]

In a similar spirit to #4281, we should possibly have our own man page(s). When we don't, Debian ends up adding something of their own, which is worse than how we could probably do it and leaves other distros' packages without man page(s) for our tools.

Related hashcat discussion: hashcat/hashcat#2429

[wsandin]

I'd happy to take on this one, and ensure it gets reviewed thoroughly over feedback loops before committing.