Examine source code of Online Time Reminder

{
  "manifest_version": 2,
  "name": "Online Time Reminder",
  "version": "1.0",
  "description": "Reminds you to take breaks after being online for a while.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "about:newtab"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{757aed81-714d-4139-9633-d0468f50acd5}"
    }
  }
}