Examine source code of docsend-dl

{
  "manifest_version": 2,
  "name": "docsend-dl",
  "version": "1.0",
  "description": "Add a download button on Docsend documents",
  "icons": {},
  "content_scripts": [
    {
      "matches": [
        "https://docsend.com/view/*"
      ],
      "js": [
        "jspdf.umd.min.js",
        "content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "https://*.cloudfront.net/docs*",
    "https://docsend-prod.s3.amazonaws.com/docs/*",
    "downloads"
  ]
}