Examine source code of leetcodetimer

{
  "manifest_version": 2,
  "name": "timer",
  "version": "1.0",
  "permissions": [
    "webRequest",
    "activeTab",
    "alarms",
    "storage",
    "runtime"
  ],
  "browser_action": {
    "default_popup": "timer.html",
    "default_title": "Click to start the timer"
  },
  "description": "Adds a 20 min timer for solving leetcode problems.",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3aca210d-4f80-4bae-95e7-af2f7dec67c2}"
    }
  }
}