Examine source code of TabFocus

{
  "manifest_version": 2,
  "name": "TabFocus",
  "description": "Study timer and focus tracker inspired by Yeolpumta",
  "version": "1.1.0",
  "icons": {
    "16": "icon/16.png",
    "48": "icon/48.png",
    "128": "icon/128.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "alarms",
    "notifications",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "pthfdsa@gmail.com",
      "data_collection_permissions": {
        "optional": [],
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "TabFocus",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.google.com/*"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}