Examine source code of Webpage Word Counter

{
  "manifest_version": 2,
  "name": "Webpage Word Counter",
  "version": "1.0",
  "description": "Counts the number of words in the current webpage.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{618640c5-9afa-46cc-a829-ace037e3e823}"
    }
  }
}