Add Javadoc for DevMojo#jvmArgs

I had to set this in a sample, and it took me
a few tries to come up with the proper syntax
for passing multiple parameters as the description
of the property was completely absent

devtools/maven/src/main/java/io/quarkus/maven/DevMojo.java

@@ -246,6 +246,9 @@ public class DevMojo extends AbstractMojo {
     @Parameter
     private File workingDir;
 
+    /**
+     * Allows configuring arbitrary JVM arguments. Multiple arguments can be specified by delimiting them with a space character.
+     */
     @Parameter(defaultValue = "${jvm.args}")
     private String jvmArgs;