update specification with new fields

SPEC.md

@@ -565,9 +565,11 @@ Plugins must output a JSON object with the following keys upon a successful `ADD
 
 - `cniVersion`: The same version supplied on input - the string "1.1.0"
 - `interfaces`: An array of all interfaces created by the attachment, including any host-level interfaces:
-    - `name`: The name of the interface.
-    - `mac`: The hardware address of the interface (if applicable).
-    - `sandbox`: The isolation domain reference (e.g. path to network namespace) for the interface, or empty if on the host. For interfaces created inside the container, this should be the value passed via `CNI_NETNS`.
+    - `name` (string): The name of the interface.
+    - `mac` (string): The hardware address of the interface (if applicable).
+    - `sandbox` (string): The isolation domain reference (e.g. path to network namespace) for the interface, or empty if on the host. For interfaces created inside the container, this should be the value passed via `CNI_NETNS`.
+    - `socket_path` (string): The path of the socket that can be passed down to OCI runtimes.
+    - `pci_id` (string): The combination of vendor id and device id to uniquely identify a device.
 - `ips`: IPs assigned by this attachment. Plugins may include IPs assigned external to the container.
     - `address` (string): an IP address in CIDR notation (eg "192.168.1.3/24").
     - `gateway` (string): the default gateway for this subnet, if one exists.