Examine source code of NPM Version Stats

{
  "manifest_version": 2,
  "name": "NPM Version Stats",
  "description": "Show npm package version usage statistics inline on the npmjs.com package page in the versions tab",
  "version": "1.0.3",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "96": "icon/96.png",
    "128": "icon/128.png"
  },
  "permissions": [
    "activeTab",
    "https://www.npmjs.com/package/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@npm-version-stats",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.npmjs.com/package/*"
      ],
      "css": [
        "content-scripts/content.css"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}