add rocksdb parallelism threads config option

Signed-off-by: strawberry <strawberry@puppygock.gay>

conduwuit-example.toml

@@ -256,6 +256,10 @@ allow_check_for_updates = true
 # Time in seconds before RocksDB will forcibly rotate logs. Defaults to 0.
 #rocksdb_log_time_to_roll = 0
 
+# Amount of threads that RocksDB will use for parallelism. Set to 0 to use all your CPUs.
+# Defaults to your CPU count divided by 2 (half)
+#rocksdb_parallelism_threads = 0
+
 
 
 ### Presence