curl_version_info: offer quic (and h3) library info

Closes #4216

include/curl/curl.h

@@ -2762,7 +2762,8 @@ typedef struct {
   unsigned int nghttp2_ver_num; /* Numeric nghttp2 version
                                    (MAJOR << 16) | (MINOR << 8) | PATCH */
   const char *nghttp2_version; /* human readable string. */
-
+  char *quic_version;          /* human readable quic (+ HTTP/3) library +
+                                  version or NULL */
 } curl_version_info_data;
 
 #define CURL_VERSION_IPV6         (1<<0)  /* IPv6-enabled */