Fixed docs format

docs/modules/ROOT/pages/index.adoc

@@ -16,14 +16,15 @@ If you are planning to run the application as a native executable and parse docu
     <quarkus.native.add-all-charsets>true</quarkus.native.add-all-charsets>
 <properties>
 ----
+====
 
 == Docker
 
 When building native images in Docker using the standard Quarkus Docker configuration files some additional features need to be
 installed to support Apache POI.  Specifically font information is not included in https://developers.redhat.com/products/rhel/ubi[Red Hat's ubi-minimal images].  To install it
 simply add these lines to your `DockerFile.native` file:
 
-[source]
+[source, dockerfile]
 ----
 FROM registry.access.redhat.com/ubi8/ubi-minimal:8.9
 
@@ -48,10 +49,6 @@ CMD ["./application", "-Dquarkus.http.host=0.0.0.0"]
 
 CAUTION: Make sure `.dockerignore` does not exclude `.so` files!
 
-
-====
-
-
 == Prerequisites
 
 To complete this guide, you need: