Examine source code of AltPkg

{
  "manifest_version": 2,
  "name": "AltPkg",
  "description": "A free and open-source extension to change the default install command on npmjs.com",
  "version": "1.2.0",
  "short_name": "AltPkg",
  "icons": {
    "16": "/icons/16.png",
    "32": "/icons/32.png",
    "48": "/icons/48.png",
    "128": "/icons/128.png"
  },
  "permissions": [
    "storage"
  ],
  "author": "Uncore",
  "browser_action": {
    "default_title": "AltPkg",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.npmjs.com/package/*"
      ],
      "run_at": "document_end",
      "js": [
        "content-scripts/content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d5dc4a73-1979-4699-94e8-300e1f8d682f}"
    }
  }
}