Examine source code of Libbification

{
  "name": "Libbification",
  "description": "Press Ctrl+Shift+U to send an event (Command+Shift+U on a Mac).",
  "manifest_version": 2,
  "version": "1.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "payghamgir@pm.me",
      "strict_min_version": "60.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "toggle-feature": {
      "suggested_key": {
        "default": "Ctrl+Shift+U"
      },
      "description": "Send a 'toggle-feature' event to the extension"
    }
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "permissions": [
    "*://librarypoint.overdrive.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "libbification.js"
      ]
    }
  ]
}