Examine source code of Focus in Read

{
  "manifest_version": 2,
  "name": "Focus in Read",
  "description": "It helps you focus on the text and read faster by showing it one word at a time at the selected speed.",
  "version": "1.3",
  "icons": {
    "128": "icon.png"
  },
  "permissions": [
    "contextMenus",
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f4daf5a4-6ed3-42c2-a73d-d8346400e2f2}"
    }
  }
}