Examine source code of pfcrypto

{
  "name": "pfcrypto",
  "short_name": "personal finance crypto tracker",
  "version": "1.2.0",
  "manifest_version": 2,
  "description": "cryptocurrency holdings updater",
  "icons": {
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "https://home.personalcapital.com/page/login/app*",
    "https://home.personalcapital.com/api/*",
    "https://api.alternative.me/v1/ticker/",
    "https://api.blockcypher.com/v1/*",
    "https://api.ethplorer.io/getAddressInfo/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://home.personalcapital.com/page/login/app*"
      ],
      "js": [
        "personalcapital.js"
      ],
      "run_at": "document_idle"
    }
  ]
}