Examine source code of ff2mpv (for Windows)

{
  "manifest_version": 3,
  "name": "ff2mpv (for Windows)",
  "description": "Also tries to play links in MPV. Adapted for Windows.",
  "version": "2.2",
  "icons": {
    "16": "icons/icon_16.png",
    "32": "icons/icon_32.png",
    "48": "icons/icon_48.png",
    "64": "icons/icon_64.png",
    "128": "icons/icon_128.png"
  },
  "action": {
    "default_icon": {
      "16": "icons/icon_16.png",
      "32": "icons/icon_32.png"
    },
    "default_title": "Play the current URL in MPV"
  },
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+Space"
      }
    }
  },
  "background": {
    "scripts": [
      "ff2mpv.js"
    ]
  },
  "permissions": [
    "contextMenus",
    "activeTab",
    "scripting"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "ff2mpv@eastmarch.github.com",
      "strict_min_version": "109.0"
    }
  }
}