add: [network-socket] Added MAC address attributes

- Even though they are not exactly part of the
  socket fields, it could be interesting to have
  them to have the information about them like
  they are described within the packets that are
  sent using the socket

objects/network-socket/definition.json

@@ -172,6 +172,16 @@
       "misp-attribute": "datetime",
       "ui-priority": 1
     },
+    "mac-dst": {
+      "description": "Destination MAC address as it is included in the packets sent",
+      "misp-attribute": "mac-address",
+      "ui-priority": 1
+    },
+    "mac-src": {
+      "description": "Source (local) MAC address as it is included in the packets sent",
+      "misp-attribute": "mac-address",
+      "ui-priority": 1
+    },
     "option": {
       "description": "Option on the socket connection.",
       "misp-attribute": "text",