Examine source code of Square Twitter PFPs

{
  "manifest_version": 2,
  "name": "Square Twitter PFPs",
  "version": "1.8",
  "description": "i made this cuz i like when pfps go square",
  "icons": {
    "48": "xafter.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*",
        "*://mobile.twitter.com/*",
        "*://x.com/*",
        "*://mobile.x.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "xafter.png"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "square-twitter-pfps@example.com",
      "strict_min_version": "109.0"
    }
  }
}