Examine source code of RandomTab

{
  "manifest_version": 2,
  "name": "RandomTab",
  "version": "1.1",
  "description": "Select an existing tab at random and make active.  Ctrl-Shift-Y does the same from the keyboard.  Alt-click on the toolbar icon or Ctrl-Shift-M selects an existing tab that is playing audio. (Shift-click on the toolbar icon will delete an existing tab at random.)",
  "homepage_url": "https://blueslugs.com",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "select-random": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y"
      },
      "description": "Select random tab"
    },
    "select-audible": {
      "suggested_key": {
        "default": "Ctrl+Shift+M"
      },
      "description": "Select random tab playing audio"
    }
  },
  "browser_action": {
    "default_icon": "icons/rt.svg",
    "default_title": "RandomTab"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{58bbfc18-9e8a-4c21-89e0-74a14dc200ff}",
      "strict_min_version": "42.0"
    }
  }
}