build: Update README.adoc [skip ci]

Author: grigala

README.adoc

@@ -1,5 +1,13 @@
 = Helloworld in Java
 
+ifdef::env-github[]
+:tip-caption: :bulb:
+:note-caption: :information_source:
+:important-caption: :heavy_exclamation_mark:
+:caution-caption: :fire:
+:warning-caption: :warning:
+endif::[]
+
 This repository shows how to configure link:https://github.com/features/actions[GitHub Actions] and link:https://jreleaser.org/[JReleaser] to:
 
  * compile a helloworld app with bundled Java Runtimes using jlink for: