update readme with --leader-election-namespace flag

README.md

@@ -53,6 +53,8 @@ Note that the external-provisioner does not scale with more replicas. Only one e
 
 * `--leader-election-type`: The resource type to use for leader election, options are 'endpoints' (default) or 'leases' (recommended)
 
+* `--leader-election-namespace`: Namespace where leader election object will be created. It is recommended that this parameter is populated from Kubernetes DownwardAPI with the namespace where the external-provisioner runs in.
+
 * `--timeout <duration>`: Timeout of all calls to CSI driver. It should be set to value that accommodates majority of `ControllerCreateVolume` and `ControllerDeleteVolume` calls. See [CSI error and timeout handling](#csi-error-and-timeout-handling) for details. 15 seconds is used by default.
 
 * `--retry-interval-start <duration>` - Initial retry interval of failed provisioning or deletion. It doubles with each failure, up to `--retry-interval-max` and then it stops increasing. Default value is 1 second. See [CSI error and timeout handling](#csi-error-and-timeout-handling) for details.