libcurl example using DOH

simple-doh.c

#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
  CURL *curl;
  CURLcode res;

  curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://curl.haxx.se/");
    curl_easy_setopt(curl, CURLOPT_DOH_URL,
                     "https://dns.cloudflare.com/.well-known/dns-query");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
  return 0;
}