Update contributors list

Author: janodvarko

package.json

@@ -7,7 +7,8 @@
   "contributors": [
     "Jan Odvarko (Mozilla Corp.)",
     "Helen V. Holmes (Mozilla Corp.)",
-    "Florent Fayolle"
+    "Florent Fayolle",
+    "Elad Zelingher"
   ],
   "license": "BSD-3-Clause",
   "icon": "chrome://websocketmonitor/skin/icon-32-color.png",