Examine source code of Time Tracker for Tabs

{
  "manifest_version": 2,
  "name": "Time Tracker for Tabs",
  "version": "1.2",
  "description": "Tracker for time spent on websites",
  "icons": {
    "96": "icons/icon96.png"
  },
  "permissions": [
    "tabs",
    "storage",
    "alarms"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/96.png",
    "default_popup": "popup/popup.html"
  },
  "applications": {
    "gecko": {
      "id": "{a7ff2a56-c420-419e-8148-e037a38416be}",
      "strict_min_version": "58.0"
    }
  }
}