Add @springio/asciidoctor-extensions/javadoc-extension

See gh-41605

antora-playbook.yml

@@ -52,6 +52,7 @@ asciidoc:
   attributes:
     chomp: all
     hide-uri-scheme: '@'
+    javadoc-location: xref:api:java/
     page-pagination: ''
     page-stackoverflow-url: https://stackoverflow.com/tags/spring-boot
     tabs-sync-option: '@'
@@ -59,6 +60,7 @@ asciidoc:
   - '@asciidoctor/tabs'
   - '@springio/asciidoctor-extensions'
   - '@springio/asciidoctor-extensions/configuration-properties-extension'
+  - '@springio/asciidoctor-extensions/javadoc-extension'
   - '@springio/asciidoctor-extensions/section-ids-extension'
 urls:
   latest_version_segment: ''