Mention that `deno-dns` is not implemented

[oxcabe]

The README.md file states that Deno is supported:

dns-records/README.md

Line 10 in 7e58d04

* Works in all JavaScript runtimes: Browsers, Node.js, CloudFlare Workers, Deno, Bun, etc

But it seems that is not implemented yet:

dns-records/src/index.ts

Lines 93 to 95 in 7e58d04

	} else if (resolver === 'deno-dns') {
	throw new Error('Deno DNS not yet implemented')
	}

I understand that it could be possible to make this library work in Deno through its Node compatibility layer. That said, the README.md file should, still, mention that the pure Deno implementation (using Deno.resolveDns) is a work in progress.

Finally, I will probably implement a Deno-only util module for retrieving DNS records and perform subdomain enumeration in a few days. I'm more than happy to ping back so you can use the code here.