Examine source code of Site timer

{
  "name": "Site timer",
  "version": "1.0.0",
  "manifest_version": 2,
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "popup.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "48": "icon.svg"
    },
    "default_title": "Site timer",
    "default_popup": "popup.html"
  },
  "permissions": [
    "<all_urls>",
    "notifications",
    "tabs",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5c04d3a2-4e0d-48e5-adeb-e774dee7b67a}"
    }
  }
}