update volume_mount docs

website/content/docs/job-specification/volume_mount.mdx

@@ -26,6 +26,7 @@ job "docs" {
       volume_mount {
         volume      = "certs"
         destination = "/etc/ssl/certs"
+        propagation_mode = "private"
       }
     }
   }
@@ -48,6 +49,11 @@ updates to remove a volume that it depends on.
   specify that it is `read_only` on a per mount level using the `read_only`
   option here.
 
+- `propagation_mode` `(string: "")` - Configure [docker bind propagation](https://docs.docker.com/storage/bind-mounts/#configure-bind-propagation),
+   Can be one of `private`、`host-to-task` or `bidirectional` . Empty string and 
+   `private` maps to `rprivate`,  `host-to-task` maps to `rslave`, 
+   and `bidirectional` maps to `rshared`.
+
 For examples of how to use [HCL2] interpolation for fine-grained control of
 volumes, see [Volume Interpolation].