Examine source code of Mirrorr

{
  "manifest_version": 2,
  "name": "Mirror",
  "version": "1.0",
  "description": "Расширение с боковой панелью",
  "permissions": [],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Mirror",
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png"
    },
    "default_popup": "index.html"
  },
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1c4bbf98-3c9d-477e-afa1-698b32a2978a}"
    }
  }
}