Examine source code of Clean Old Reddit

{
  "name": "Clean Old Reddit",
  "description": "Clean up old Reddit for lurkers",
  "version": "1.0.1",
  "manifest_version": 3,
  "content_scripts": [
    {
      "matches": [
        "*://old.reddit.com/*"
      ],
      "css": [
        "main.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF}"
    }
  }
}