You have explicitly asked your code to ignore any kind of certificate validation, with “rejectUnauthorized” set to “false”.
You are passing the “Host:” header “cdn.jsdelivr.net” to Cloudflare, within the “headers {}” block you have.
As you are ignoring certificate validations, “servername” does not matter for the TLS connection any more.
Once the requests hits Cloudflare, Cloudflare will select the appropriate content based on the “Host:” header, which in your case, is (still) “cdn.jsdelivr.net”.
There is no feature, and nothing to enable here.
Same will happen for every website, when you disable certificate validation, and (still) supply a correct “Host:” header, matching a valid virtual host configuration in the given web server you’re connecting to.