Add Eclipse Austen as a project to the WG site

The project Eclipse Austen currently being setup/created. https://projects.eclipse.org/proposals/eclipse-austen

Once it is ready, it should be on the WG's project list: https://asciidoc-wg.eclipse.org/projects/

@abelsromero - could you please take on this task once Eclipse Austen should appear on the WG's site?

Content goes here: https://github.com/EclipseFdn/asciidoc-wg.eclipse.org/tree/main/content/projects The Hugo setup would require a new folder austen as a sibling to the folder asciidoc-lang with similar content.

Thanks!