Examine source code of Old Reddit Beautifier

{
  "manifest_version": 2,
  "name": "Old Reddit Beautifier",
  "version": "1.0",
  "description": "Enhances the appearance of old Reddit pages",
  "permissions": [
    "https://old.reddit.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://old.reddit.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{74120cd9-39b0-40b9-b937-7dc290f1f52a}"
    }
  }
}