Examine source code of Restmail Inbox

{
  "manifest_version": 2,
  "name": "Restmail Inbox",
  "version": "1.0",
  "description": "Fetch and view emails from restmail.net",
  "permissions": [
    "storage",
    "activeTab",
    "https://restmail.net/*"
  ],
  "icons": {
    "48": "icons/icon.ico"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon.ico"
  },
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "58.0",
      "id": "{cce6e967-6cf7-4198-a44b-c024e5274ec0}"
    }
  }
}