Supports DocBook 5 and man page backends

[sorairolake]

Asciidoctor supports HTML5 as a backend, as well as DocBook 5 and man page. So I think it would be useful for Asciidork to have DocBook 5 and man page backends.

[jaredh159]

@sorairolake hey, sorry for the delay getting back to you, i didn't have notifications turned on for this repo, so completely missed that you opened this issue.

yes, i definitely agree, and it should be possible to write backends for these (and more), and eventually I'd love to either do it myself or merge a PR. you have any interest in working on this?

i'm curious, are you using Asciidork in any way, or just experimenting with it? thanks again, and sorry for the delay!