Examine source code of play-url

{
  "name": "play-url",
  "version": "0.1.0",
  "description": "Send a m3u containing the active URL",
  "manifest_version": 2,
  "browser_action": {
    "browser_style": true,
    "default_title": "play-url",
    "default_icon": "icons/play-url.svg",
    "theme_icons": [
      {
        "light": "icons/play-url-light.svg",
        "dark": "icons/play-url-dark.svg",
        "size": 32
      }
    ]
  },
  "icons": {
    "16": "icons/play-url.svg",
    "32": "icons/play-url.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "play": {
      "description": "play-url"
    }
  },
  "permissions": [
    "activeTab",
    "contextMenus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c708a209-85b1-45fd-b98f-655979793717}"
    }
  }
}