Add link to issue tracker for the AsciiDoc WG

Created by: mojavelinux

The AsciiDoc WG now has it's own issue tracker located at https://gitlab.eclipse.org/eclipse-wg/asciidoc-wg/asciidoc-wg/-/issues. Since this website is meant to be a portal for all orders of business of the AsciiDoc WG, I think it should be possible to navigate to this issue tracker from the website.

What I'm not sure yet is where this link would go. It would make sense for it to be shown next to the link for the mailing list. However, that link to the mailing list isn't currently in the navigation hierarchy. I suppose we could put it below the mailing list link on the home page, but that could look too busy.

Instead, I think we need a new item in the navigation somewhere named "Participate". This heading is consistent with Eclipse's own working group home page. Under this heading could be "Mailing list", "Issue tracker", and perhaps other communication channels in the future. I would even be open to putting the Participate heading under a "More" entry in the navbar if it's taking up too much space.

For examples, see https://www.eclipse.org/org/workinggroups/ and https://edgenative.eclipse.org/