Examine source code of Freedom - Website Blocker

{
  "manifest_version": 2,
  "name": "Freedom - Website Blocker for Firefox",
  "description": "The Freedom website blocker gives you control over distracting websites, so you can focus on what matters most.",
  "homepage_url": "https://freedom.to/",
  "version": "17.0.12",
  "icons": {
    "128": "images/icon128.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://*/*",
    "storage",
    "notifications"
  ],
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "128": "images/icon128.png"
    },
    "default_title": "Freedom",
    "default_popup": "html/popup.html"
  }
}