Examine source code of Downie Extension

{
  "background": {
    "service_worker": "background.js",
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_icon": "icon32.png",
    "default_title": "Open With Downie",
    "theme_icons": [
      {
        "dark": "icon32.png",
        "light": "icon32.png",
        "size": 32
      }
    ]
  },
  "commands": {
    "XUOpenCurrentSite": {
      "description": "Open current site with Downie.",
      "suggested_key": {
        "default": "MacCtrl+Shift+D"
      }
    }
  },
  "description": "Sends current page to Downie.",
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "manifest_version": 3,
  "name": "Downie",
  "permissions": [
    "contextMenus",
    "tabs",
    "storage"
  ],
  "host_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "version": "1.3.2",
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "downie@charliemonroe.net",
      "strict_min_version": "123.0"
    }
  }
}