Docs: Make Java build version more prominent.

docs/content/documentation/contributors/buildingelk.md

@@ -9,9 +9,9 @@ menu:
 
 ELK is built using [Apache Maven](https://maven.apache.org/) in conjunction with [Tycho](https://eclipse.org/tycho/) to tell Maven how to build Eclipse projects. There are two parts that can be built: the Eclipse Layout Kernel itself, and the metadata compiler used by the main ELK build. The remainder of this page assumes that you have opened a shell in the `build/` directory inside your clone of the ELK repository.
 
-## Build Requirements
-
+{{% note title="A Quick Warning" mode="warning" %}}
 Building ELK currently requires Java 8 and _will not_ work with more recent Java versions. We use Maven 3.6, but other versions will probably work just as well.
+{{% /note %}}
 
 
 ## Building ELK