Merge pull request #15 from redpanda-data/Add-link-to-asciidoc-docs

Add link to Asciidoc docs

meta-docs/CONTRIBUTING.adoc

@@ -10,6 +10,7 @@
 :url-netlify-docs: https://docs.netlify.com
 :url-antora-docs: https://docs.antora.org
 :url-redoc: https://github.com/Redocly/redoc
+:url-asciidoc: https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/
 :idprefix:
 :idseparator: -
 :experimental:
@@ -413,4 +414,4 @@ Each message shows the repository source, the refname, and the path from the roo
 
 == Contact us
 
-Get in touch with the Redpanda docs team on https://redpanda.com/slack[Slack] in the #docs channel.
+Get in touch with the Redpanda docs team on https://redpanda.com/slack[Slack] in the #docs channel.