Examine source code of eBird sharing link

{
  "manifest_version": 2,
  "name": "eBird sharing link",
  "version": "1.0.0",
  "content_scripts": [
    {
      "matches": [
        "https://ebird.org/*checklist/*"
      ],
      "js": [
        "shareLink.js"
      ]
    }
  ],
  "description": "eBird sharing link",
  "homepage_url": "https://www.faintlake.com/eBird/extension/SharingURL",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png"
  }
}