Examine source code of Prefer Following

{
  "manifest_version": 2,
  "name": "Prefer Following",
  "version": "1.1",
  "description": "An extension that clicks to Following tab for you everytime you refresh Twitter.",
  "content_scripts": [
    {
      "matches": [
        "*://*.twitter.com/*"
      ],
      "js": [
        "twitter.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{58ccd637-139c-4e96-82e4-34a93724ef7a}"
    }
  }
}