Examine source code of One True Check

{
  "manifest_version": 2,
  "name": "One True Check: Twitter Legacy Verified Users",
  "short_name": "OTC",
  "version": "1.1.0",
  "description": "An unopinionated tool that displays a checkmark next to the name of each user who was verified with Twitter's legacy system.",
  "author": "One True Check",
  "homepage_url": "https://onetruecheck.com",
  "icons": {
    "16": "public/icon-16.png",
    "24": "public/icon-24.png",
    "32": "public/icon-32.png",
    "48": "public/icon-48.png",
    "96": "public/icon-96.png",
    "128": "public/icon-128.png",
    "256": "public/icon-256.png"
  },
  "web_accessible_resources": [
    "public/*",
    "assets/*",
    "content/index.js.map"
  ],
  "permissions": [
    "storage"
  ],
  "background": {
    "scripts": [
      "background/index.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup/index.html",
    "default_icon": {
      "16": "public/icon-16.png",
      "24": "public/icon-24.png",
      "32": "public/icon-32.png",
      "48": "public/icon-48.png",
      "96": "public/icon-96.png",
      "128": "public/icon-128.png",
      "256": "public/icon-256.png"
    },
    "default_title": "One True Check: Twitter Legacy Verified Users"
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*",
        "*://*.twitter.com/*",
        "https://extensionpay.com/*"
      ],
      "js": [
        "content/index.js"
      ],
      "css": [
        "content/index.css"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{398fc06d-6f66-44d8-801c-34d9f49b1922}"
    }
  }
}