Examine source code of PNL Reader: read quietly or read aloud

{
  "description": "Read any webpage quietly with dark mode, artistic fonts or read it aloud with natural sounding voices 📖",
  "version": "2.8.1",
  "manifest_version": 2,
  "name": "PNL Reader: read quietly or read aloud",
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.bundle.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://pnl.dev/*"
      ],
      "js": [
        "inject-pdf-reader.bundle.js",
        "inject-reader-customization.bundle.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "icons": {
    "32": "images/logo32.png",
    "48": "images/logo48.png",
    "128": "images/logo128.png"
  },
  "web_accessible_resources": [
    "images/*.png"
  ],
  "browser_action": {
    "default_title": "PNL Reader: read quietly or read aloud"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8a1b9de7-0601-4ccb-93b8-3f60fa7a5772}",
      "data_collection_permissions": {
        "required": [
          "authenticationInfo",
          "websiteActivity"
        ]
      }
    }
  }
}