Examine source code of Session Manager Pro

{
  "manifest_version": 2,
  "name": "Session Manager Pro",
  "version": "1.2.0",
  "description": "Multiple login sessions for any site - like SessionBox",
  "permissions": [
    "tabs",
    "storage",
    "cookies",
    "<all_urls>",
    "contextualIdentities"
  ],
  "icons": {
    "48": "icons/icon-48.svg",
    "96": "icons/icon-96.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Session Manager Pro",
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.svg",
      "96": "icons/icon-96.svg"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{28dbeb63-b8ca-46a3-b3b1-0427084f0e81}",
      "strict_min_version": "58.0"
    }
  }
}