I think the problem is that the package has not been build for the browser. You cannot require the cjs module because it’s not Node.js, and you cannot import the ES module either (with import('https://unpkg.com/@mycrypto/eth-scan@2.1.0/lib/es/index.js?module') for example) because various dependencies don’t publish an ES module, such as https://unpkg.com/isomorphic-unfetch@3.0.0?module.