Add support for rouge code highlighter

[jljouannic]

Jekyll has dropped support for Pygments in the recent 4.0 release.

The jekyll-asciidoc plugin still relies on Pygments for code styling.

As an asciidoctor-rouge gem already exists, I wonder how difficult it would be to add support for it in the plugin, so that Pygment would not be needed anymore.

[mojavelinux]

The jekyll-asciidoc plugin doesn't rely on Pygments for code styling. It just happens to generate the stylesheet for Pygments and copy it to the output. The same could be done for Rouge.

You can certainly use Rouge with jekyll-asciidoc today. First, set source-highlighter to rouge. Then, either set rouge-css to style or put the stylesheet in generated site yourself.

All the plugin would do is generate a copy the stylesheet for you. And we could certainly add that. You can find the logic in this file: https://github.com/asciidoctor/jekyll-asciidoc/blob/master/lib/jekyll-asciidoc/integrator.rb

[mojavelinux]

As an asciidoctor-rouge gem already exists

Do not use that. Asciidoctor has support for Rouge out of the box starting in 2.0.