Add controls for influencing Matrix Synapse's rate-limiting

roles/matrix-server/defaults/main.yml

@@ -61,6 +61,10 @@ matrix_synapse_max_upload_size_mb: 10
 matrix_synapse_max_log_file_size_mb: 100
 matrix_synapse_max_log_files_count: 10
 
+# Rate limits
+matrix_synapse_rc_messages_per_second: 0.2
+matrix_synapse_rc_message_burst_count: 10.0
+
 # A list of additional "volumes" to mount in the container.
 # This list gets populated dynamically based on Synapse extensions that have been enabled.
 # Contains definition objects like this: `{"src": "/outside", "dst": "/inside", "options": "rw|ro|slave|.."}