Examine source code of Toolbar Clockca

{
  "version": "0.1.1",
  "manifest_version": 2,
  "name": "Toolbar Clock",
  "offline_enabled": true,
  "short_name": "toolbar-clock",
  "permissions": [
    "storage",
    "contextMenus"
  ],
  "background": {
    "page": "lib/chrome/background.html"
  },
  "description": "Stylish analog clock in your browser toolbar.",
  "homepage_url": "https://mybrowseraddon.com/toolbar-clock.html",
  "browser_action": {
    "default_title": "Toolbar Clock",
    "default_popup": "data/popup/popup.html",
    "default_icon": {
      "16": "data/icons/16.png",
      "32": "data/icons/32.png",
      "48": "data/icons/48.png",
      "64": "data/icons/64.png"
    }
  },
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{57066283-c918-49f8-9fc5-35eb792a1af7}"
    }
  }
}