Examine source code of Digital Clock

{
  "manifest_version": 2,
  "name": "Digital Clock",
  "description": "A digital clock for the browser",
  "version": "1.2",
  "default_locale": "en",
  "browser_action": {
    "default_popup": "options.html"
  },
  "background": {
    "page": "background.html"
  },
  "permissions": [
    "storage"
  ]
}