Examine source code of OldRedditSwitcheroo

{
  "manifest_version": 2,
  "name": "OldRedditSwitcheroo",
  "version": "1.0",
  "description": "Redirects all reddit links to old.reddit.com, rather than the redesigned site.",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.reddit.com/*"
      ],
      "js": [
        "switcheroo.js"
      ]
    }
  ]
}