Examine source code of Micro Timer

{
  "manifest_version": 2,
  "name": "Micro Timer",
  "version": "1.0",
  "description": "A tiny countdown timer to limit browsing time on specific sites.",
  "permissions": [
    "storage",
    "alarms",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Micro Timer",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8dfd40d6-f83b-4724-b464-f7168d171158}"
    }
  }
}