New mkdocs-asciidoctor-backend plugin

[aireilly]

Hi, I created a new plugin for Material for MkDocs: https://pypi.org/project/mkdocs-asciidoctor-backend/

This plugin allows you to use AsciiDoc format docs alongside Markdown, building HTML using an Asciidoctor server the Asciidoctor Ruby CLI.

Have a look, let me know what you think.

[aireilly]

Changed the plugin to run an Asciidoctor Ruby server instead of spinning up the Asciidoctor CLI individually for AsciiDoc files.

Testing on a reasonably large AsciiDoc site with 1470 AsciiDoc files, build time was reduced from 56.35 seconds to 18.43 seconds.