docs: add fluentd write timeout log driver option

Signed-off-by: Austin Vazquez <[email protected]>

Author: austinvazquez

content/manuals/engine/logging/drivers/fluentd.md

@@ -143,6 +143,11 @@ The maximum number of retries. Defaults to `4294967295` (2\*\*32 - 1).
 
 Generates event logs in nanosecond resolution. Defaults to `false`.
 
+### fluentd-write-timeout
+
+Sets the timeout for the write call to the Fluentd daemon. By default,
+writes have no timeout and will block indefinitely.
+
 ## Fluentd daemon management with Docker
 
 About `Fluentd` itself, see [the project webpage](https://www.fluentd.org)