Add new example for IPv6 with UDP

examples/hello_client_v6_udp.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <errno.h>
+
+#define SOCK_IMPLEMENTATION
+#include "sock.h"
+
+int main(void)
+{
+    bool err = false;
+
+    Sock *s = sock_create(SOCK_IPV6, SOCK_UDP);
+    if (s == NULL) { err = "create"; goto defer; }
+
+    SockAddr addr = sock_addr("::1", 6969);
+
+    const char *msg = "Hello from client!";
+    char buf[128];
+    memset(buf, 0, sizeof(buf));
+
+    sock_sendto(s, msg, strlen(msg), addr);
+    sock_recvfrom(s, buf, sizeof(buf), NULL);
+
+    printf("%s:%d: %.*s\n", addr.str, addr.port,
+            (int)sizeof(buf), buf);
+
+defer:
+    if (err) sock_log_error(s);
+    sock_close(s);
+
+    return 0;
+}