Examine source code of txtify.it

{
  "author": "Dmitry",
  "manifest_version": 2,
  "name": "txtify.it",
  "version": "1.1.0",
  "description": "Convert web articles to plain text using https://txtify.it/",
  "browser_action": {
    "default_title": "txtify it!",
    "default_icon": {
      "16": "icons/icon16.png",
      "24": "icons/icon24.png",
      "32": "icons/icon32.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "96": "icons/icon96.png",
    "128": "icons/icon128.png"
  },
  "background": {
    "scripts": [
      "app.js"
    ],
    "persistent": true
  },
  "options_ui": {
    "page": "options/index.html"
  },
  "permissions": [
    "storage",
    "tabs",
    "activeTab",
    "<all_urls>",
    "contextMenus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{72d81803-ba86-45e8-aae6-1629f0c51834}"
    }
  }
}