(node:557) UnhandledPromiseRejectionWarning: Error: unable to get local issuer certificate

I just installed with `npm install ytdl-core@latest`, created an index.js that contains the "Usage" example in the readme, and ran
```
% node index.js
(node:557) UnhandledPromiseRejectionWarning: Error: unable to get local issuer certificate
at TLSSocket.onConnectSecure (_tls_wrap.js:1515:34)
at TLSSocket.emit (events.js:400:28)
at TLSSocket._finishInit (_tls_wrap.js:937:8)
at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:709:12)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:557) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:557) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
```

Reproduce the report by installing ytdl-core@latest, copying the README Usage example into index.js, and running it with Node. Start by checking whether the certificate error occurs with the repository's current example or only in the reported environment; done means the cause is established and any needed project change or documentation gap is clearly identified.

Written by the indexing model from the issue text.