RFS: new version of asciidoctor ready for review/upload

[Joseph Herlant <herlantj@gmail.com>]

Hi guys,

I've updated the asciidoctor package with the latest 1.5.7 release
from 3 days ago.
It is available in https://salsa.debian.org/ruby-team/asciidoctor

Could you have a look when you have a moment to review the changes please?

Thanks for your help,
Joseph