Add note on return value of dns.resolve

src/native-dns.js

@@ -27,6 +27,9 @@ function resolve(hostname, rrtype, options, callback) {
     resolver.resolve(hostname, rrtype, function (error, result) {
         clearTimeout(timerId);
 
+        // result is an empty array if there was no error but there is no record. when you query a random
+        // domain, it errors with ENOTFOUND. But if you query an existing domain (A record) but with different
+        // type (CNAME) it is not an error and empty array
         callback(error, result);
     });
 }