Document Docker dependency on README

Signed-off-by: edu <bfwaend@gmail.com>

README.adoc

@@ -148,7 +148,7 @@ https://github.com/spring-projects/spring-data-jpa/issues[issue tracker] to see
 == Building from Source
 
 You don’t need to build from source to use Spring Data (binaries in https://repo.spring.io[repo.spring.io]), but if you want to try out the latest and greatest, Spring Data can be easily built with the https://github.com/takari/maven-wrapper[maven wrapper].
-You also need JDK 17 or above.
+You also need JDK 17 or above and Docker for integration tests.
 
 [source,bash]
 ----