Track open issues in other projects

[hepabolu]

The sole purpose for this issue is to track issues I opened in other projects, so I have all of them together and don't have to hunt my ginormous list of open tabs.

• Vale project, ignore variables: Vale configuration in GitHub Actions for asciidoctor files errata-ai/vale-action#11
• Asciidoctor, Rouge, linenums: Implement support for rouge-linenums-mode (add inline mode) asciidoctor/asciidoctor#3641

Tracking other interesting issues as well

• index in ePub: index not generated asciidoctor/asciidoctor-epub3#168
• index in HTML: Output index when using HTML5 backend (like a2x) asciidoctor/asciidoctor#450
• remote urls in ePub manifest: Remote image/audio/video URLs need to be included in manifest asciidoctor/asciidoctor-epub3#334

[hepabolu]

I will close this issue as the issues I'm tracking are not going to end up in the first official release