Examine source code of Focus To Read

{
  "name": "Focus To Read",
  "version": "1.7.0",
  "manifest_version": 2,
  "description": "Make page easy to read",
  "icons": {
    "48": "icons/48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "icons/32.png",
    "default_title": "Click to select an element to make it easy to read"
  }
}