Examine source code of Toolbar Clock

{
  "manifest_version": 2,
  "name": "Toolbar Clock",
  "version": "1.1.0",
  "description": "Shows an analog clock icon and opens a digital clock popup.",
  "permissions": [
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true,
    "browser_style": false
  },
  "browser_action": {
    "default_title": "Current time",
    "default_icon": "icons/clock.svg",
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icons/clock.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "toolbar-clock@md2perpe.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}