Examine source code of Clock Dynamic Theme

{
  "manifest_version": 2,
  "name": "Clock Dynamic Theme",
  "version": "0.1",
  "description": "A dynamic theme with clock",
  "homepage_url": "https://colorfox.jackjyq.com/",
  "permissions": [
    "alarms",
    "theme"
  ],
  "icons": {
    "48": "icon@48.png",
    "96": "icon@96.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "strict_min_version": "55.0a2"
    }
  }
}