Examine source code of LeetPlug

{
  "manifest_version": 2,
  "name": "LeetPlug",
  "description": "This extension adds tracking features to the LeetCode interface.",
  "version": "1.1.1",
  "icons": {
    "16": "images/brain16.png",
    "24": "images/brain24.png",
    "32": "images/brain32.png",
    "128": "images/brain128.png"
  },
  "browser_action": {
    "default_icon": "images/brain24.png",
    "default_popup": "src/popup.html"
  },
  "permissions": [
    "storage",
    "*://leetplug.azurewebsites.net/*"
  ],
  "background": {
    "scripts": [
      "src/background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "https://leetcode.com/problems/*"
      ],
      "run_at": "document_start",
      "js": [
        "thirdParty/jquery-3.5.1.slim.min.js",
        "src/problemsScript.js"
      ]
    }
  ]
}