Examine source code of Language Labeler

{
  "manifest_version": 2,
  "name": "Language Labeler",
  "version": "1.0",
  "description": "Tag vocabulary by topic.",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0101e3f2-9ec6-4eef-83c7-16b3b3244e4c}"
    }
  }
}