Examine source code of av.by

{
  "manifest_version": 2,
  "name": "av.by",
  "version": "1.1",
  "description": "Added aditional fields to ads",
  "icons": {
    "48": "images/logo.svg"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>",
    "activeTab"
  ],
  "applications": {
    "gecko": {
      "id": "maksimochka200@gmail.com",
      "strict_min_version": "45.0"
    }
  },
  "background": {
    "scripts": [
      "av.js"
    ]
  },
  "web_accessible_resources": [
    "images/handshake.png"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.av.by/*",
        "*://av.by/profile/bookmarks/cars"
      ],
      "js": [
        "jquery-3.5.1.min.js",
        "content_scripts/ad.js"
      ],
      "css": [
        "content_scripts/styles/styles.css"
      ]
    }
  ]
}