Examine source code of Copy Scratch link

{
  "name": "Copy Scratch Link",
  "description": "Adds \"Copy Link\" Button to Scratch comments",
  "manifest_version": 2,
  "version": "1.1",
  "homepage_url": "https://github.com/Sly-Little-Fox",
  "icons": {
    "48": "icons/icon.svg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://scratch.mit.edu/users/*",
        "*://scratch.mit.edu/studios/*"
      ],
      "js": [
        "index.js"
      ]
    }
  ]
}