Examine source code of HideMail.app

{
  "manifest_version": 2,
  "name": "HideMail - Privacy Email Forwarding",
  "author": "Daneke George",
  "description": "It gives you unique, random email addresses that are forwarded to your email when you want keep private your personal email",
  "homepage_url": "https://hidemail.app",
  "version": "1.0.2",
  "icons": {
    "48": "img/Icon-4.png",
    "96": "img/Icon-5.png",
    "128": "img/128.png"
  },
  "browser_action": {
    "default_icon": "img/Icon-4.png",
    "default_title": "HideMail",
    "default_popup": "app.html"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "content_security_policy": "script-src 'self' ; object-src 'self'",
  "applications": {
    "gecko": {
      "id": "browser-extension@hidemail"
    }
  },
  "sidebar_action": {
    "default_icon": {
      "48": "img/Icon-4.png",
      "96": "img/Icon-5.png",
      "128": "img/128.png"
    },
    "default_title": "HideMail",
    "default_panel": "app.html"
  }
}