docs: add dest_cidr_list example and 'all' protocol to egress firewall

Author: elivlo

website/docs/r/egress_firewall.html.markdown

@@ -17,9 +17,10 @@ resource "cloudstack_egress_firewall" "default" {
   network_id = "6eb22f91-7454-4107-89f4-36afcdf33021"
 
   rule {
-    cidr_list = ["10.0.0.0/8"]
-    protocol  = "tcp"
-    ports     = ["80", "1000-2000"]
+    cidr_list      = ["10.0.0.0/8"]
+    dest_cidr_list = ["192.168.0.0/16"]
+    protocol       = "tcp"
+    ports          = ["80", "1000-2000"]
   }
 }
 ```
@@ -48,7 +49,7 @@ The `rule` block supports:
 * `dest_cidr_list` - (Optional) A CIDR list to restrict the destination of egress traffic.
 
 * `protocol` - (Required) The name of the protocol to allow. Valid options are:
-    `tcp`, `udp` and `icmp`.
+    `tcp`, `udp`, `icmp` and `all`.
 
 * `icmp_type` - (Optional) The ICMP type to allow. This can only be specified if
     the protocol is ICMP.