Add doc for mongodb_set_parameters var

Author: neilime

README.md

@@ -87,6 +87,11 @@ mongodb_replication_replset:                      # Enable replication <setname>
 mongodb_replication_replindexprefetch: "all"      # specify index prefetching behavior (if secondary) [none|_id_only|all]
 mongodb_replication_oplogsize: 1024               # specifies a maximum size in megabytes for the replication operation log
 
+## setParameter options
+# Configure setParameter option.
+# Example : 
+mongodb_set_parameters: { "enableLocalhostAuthBypass": "true", "authenticationMechanisms": "SCRAM-SHA-1,MONGODB-CR" }
+
 # MMS Agent
 mongodb_mms_agent_pkg: https://mms.mongodb.com/download/agent/automation/mongodb-mms-automation-agent-manager_1.4.2.783-1_amd64.deb
 mongodb_mms_group_id: ""