examples: add logger fields

examples/config-dev.yaml

@@ -33,6 +33,11 @@ web:
 #   signingKeys: "6h"
 #   idTokens: "24h"
 
+# Options for controlling the logger.
+# logger:
+#   level: "debug"
+#   format: "text" # can also be "json"
+
 # Instead of reading from an external storage, use this list of clients.
 #
 # If this option isn't choosen clients may be added through the gRPC API.