Add guidance for creating a Quarkus doc abstract

docs/src/main/asciidoc/doc-reference.adoc

@@ -82,8 +82,16 @@ The following links provide background on Asciidoc syntax and general convention
 :semantic-line-breaks: footnote:smbl[Rhodes, B. Semantic Linefeeds. https://rhodesmill.org/brandon/2012/one-sentence-per-line/]
 
 Text in paragraphs, lists, and tables should be broken into pieces that are easier to review{semantic-line-breaks}.
-Start a new line at the end of each sentence, and
-split sentences themselves at natural breaks between clauses.
+Start a new line at the end of each sentence, and split sentences themselves at natural breaks between clauses.
+
+=== Abstracts (preamble)
+
+For optimum findability, add a short description using user-oriented keywords to summarize the document's purpose, task, and intent in no more than three sentences.
+
+[IMPORTANT]
+====
+The first sentence of the abstract must explain the value and some benefit of the content in less than 26 words because this automatically displays on the link:https://quarkus.io/guides/[Quarkus guides homepage].
+====
 
 === Automatic Table of Contents (TOC)