Examine source code of Twitter Easy Likes

{
  "description": "Adds link to Twitter's \"Likes\" on the main Twitter page (saves you 2 click for reaching likes)",
  "manifest_version": 2,
  "name": "Twitter Easy Likes",
  "short_name": "Twitter Likes",
  "version": "0.1.2",
  "homepage_url": "https://github.com/keul/twitter-easy-likes",
  "icons": {
    "48": "icons/twitter-likes-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*",
        "*://mobile.twitter.com/*"
      ],
      "js": [
        "twt-likes.js"
      ],
      "run_at": "document_idle"
    }
  ]
}