Examine source code of LeekCF Rating

{
  "name": "LeekCF Rating",
  "description": "Get rating for Codeforces problems even with problem tags off.",
  "version": "2.1.2",
  "manifest_version": 3,
  "browser_specific_settings": {
    "gecko": {
      "id": "cf-rater@ahmadshatnawi.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "images/icon_16.png",
    "32": "images/icon_32.png",
    "48": "images/icon_48.png",
    "128": "images/icon_128.png"
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": "images/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://codeforces.com/problemset/problem/*/*",
        "*://codeforces.com/contest/*/problem/*"
      ],
      "js": [
        "background.js"
      ],
      "css": [
        "background.css"
      ]
    }
  ]
}