unpkg Link

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "name": "unpkg Link",
  "version": "2.0.0",
  "description": "Adds a link to unpkg.com for packages on npmjs.org",
  "homepage_url": "https://github.com/DrewML/unpkg-link",
  "manifest_version": 2,
  "minimum_chrome_version": "49",
  "permissions": [
    "https://www.npmjs.com/package/*"
  ],
  "content_scripts": [
    {
      "run_at": "document_idle",
      "matches": [
        "https://www.npmjs.com/package/*"
      ],
      "js": [
        "index.js"
      ]
    }
  ]
}