Examine source code of VIPKid+

{
  "manifest_version": 2,
  "name": "VIPKid+",
  "version": "1.7resigned1",
  "description": "Improves the VIPKid scheduling tool",
  "icons": {
    "16": "16.png",
    "48": "48.png",
    "128": "128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://t.vipkid.com.cn/tp/booking/course",
        "https://www.vipkidteachers.com/tp/booking/course"
      ],
      "js": [
        "VIPKid+.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_action": {
    "default_icon": "16.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{62770dc0-d4d6-40af-99bc-e1bbae9f6c2c}"
    }
  }
}