Examine source code of ExTex

{
  "manifest_version": 2,
  "name": "ExTex",
  "version": "1.0",
  "description": "Renderiza LaTeX en los mensajes de WhatsApp Web.",
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "https://web.whatsapp.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "https://web.whatsapp.com/*"
      ],
      "css": [
        "katex/katex.min.css"
      ],
      "js": [
        "katex/katex.min.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "https://web.whatsapp.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    "katex/fonts/*",
    "katex/katex.min.js",
    "katex/katex.min.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "extex@extex.com",
      "strict_min_version": "58.0"
    }
  }
}