Mark Formatter as provided, remove dependency on Arc.

Change-Id: Ia5faeefbaf541381e44c53f621d0c08ae28ec2ad
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java
index d6eeb0e..0c691b7 100644
--- a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java
@@ -17,7 +17,7 @@
  *
  * @see LogEntry
  */
-class Formatter extends ExtFormatter {
+public class Formatter extends ExtFormatter {
 
   private static final String TRACE_LEVEL = "TRACE";
   private static final String DEBUG_LEVEL = "DEBUG";