Examine source code of Reading Speed Estimator

{
  "manifest_version": 2,
  "name": "Reading Speed Estimator",
  "version": "1.0",
  "description": "Estimate reading time for web pages based on user reading speed.",
  "permissions": [
    "activeTab",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon.png"
    }
  },
  "icons": {
    "48": "icons/icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b4ce58e3-63e2-4c88-8eff-56e823e96d21}"
    }
  }
}