Quarkus: Simplify and document on/off toggle.

Change-Id: I90b5879ff99ec54deb17453af709ce2ba7070c0d
diff --git a/README.adoc b/README.adoc
index 27d8cf8..3460598 100644
--- a/README.adoc
+++ b/README.adoc
@@ -63,6 +63,14 @@
 }
 ----
 
+By default the extension is turned on.  You can turn the extension on
+or off explicitly by configuring the `quarkus.log.console.google` key
+in `application.properties`:
+
+[source,properties]
+----
+quarkus.log.console.google = true
+----
 
 == Activation (Other Frameworks)