Examine source code of Reddit User Info

{
  "manifest_version": 2,
  "name": "Reddit User Info",
  "version": "1.0",
  "description": "Shows account age and karma for Reddit users on old.reddit.com",
  "content_scripts": [
    {
      "matches": [
        "*://*.reddit.com/*",
        "*://old.reddit.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "*://*.reddit.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{9a344e0b-abd4-46a1-99c8-9afc5eaacb86}"
    }
  }
}