Examine source code of Page Word Count

{
  "manifest_version": 2,
  "name": "Page Word Count",
  "version": "1.0.0",
  "description": "Counts visible words on the current page and shows quick page stats in the popup. Runs only on the active tab after a user gesture.",
  "browser_specific_settings": {
    "gecko": {
      "id": "page-word-count@example.com",
      "strict_min_version": "91.0"
    }
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Page Word Count",
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "icons": {
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  }
}