Examine source code of TempMailPlus

{
  "manifest_version": 2,
  "short_name": "TempMail+",
  "name": "TempMailPlus",
  "description": "__MSG_appDesc__",
  "version": "0.0.34",
  "default_locale": "en",
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "icons": {
    "16": "img/16x16.png",
    "48": "img/48x48.png",
    "128": "img/128x128.png"
  },
  "background": {
    "scripts": [
      "chrome_background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_icon": "img/128x128.png",
    "default_popup": "",
    "default_title": "TempMailX"
  },
  "web_accessible_resources": [],
  "permissions": [
    "*://*.temp-mail.org/*",
    "storage",
    "notifications",
    "tabs",
    "contextMenus"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{cfddedf6-166b-4f99-86c4-543e4e1b3024}"
    }
  }
}