Examine source code of Shop-Engel

{
  "manifest_version": 2,
  "default_locale": "de",
  "name": "Shop-Engel",
  "description": "Der Shop-Engel findet automatisch Partner-Shops und erinnert Sie daran, vorher über Schulengel.de zu gehen.",
  "version": "3.6.1",
  "browser_action": {
    "default_icon": "img/icon19.png",
    "default_title": "Shop-Engel"
  },
  "permissions": [
    "webRequest",
    "tabs",
    "storage",
    "https://www.schulengel.de/",
    "https://stage.schulengel.de/"
  ],
  "icons": {
    "16": "img/icon16.png",
    "48": "img/icon48.png",
    "128": "img/icon128.png"
  },
  "background": {
    "persistent": true,
    "scripts": [
      "js/bg.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "js/contentscript.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "all_frames": false,
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    "frame.html",
    "css/content.css",
    "css/frame.css",
    "js/frame.js",
    "img/close.png",
    "img/close_white.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "extension21728@extension21728.com"
    }
  }
}