Add DNSServer library

Author: kuba2k2

platformio.ini

@@ -169,5 +169,7 @@ build_flags = ${env.build_flags}
 platform = libretiny @ ^1.9.1
 board = ${sysenv.PIO_BOARD}
 lib_deps =
+; add DNS server library for LibreTiny
+  DNSServer
   ESP32Async/AsyncTCP @ 3.4.3
 custom_versions.freertos = 9.0.0