Print out in hex format in case non printable data are received

examples/peripherals/uart_async_rxtxtasks/README.md

@@ -9,3 +9,13 @@ If you'd like to see your ESP32 receive something, simply short
 TXD_PIN and RXD_PIN. By doing this data transmitted on TXD_PIN will
 be received on RXD_PIN. See the definitions of TXD_PIN and RXD_PIN
 in ./main/uart_async_rxtxtasks_main.c.
+
+The output for such configuration will look as follows: 
+
+```
+I (3261) TX_TASK: Wrote 11 bytes
+I (4261) RX_TASK: Read 11 bytes: 'Hello world'
+I (4261) RX_TASK: 0x3ffb821c   48 65 6c 6c 6f 20 77 6f  72 6c 64                 |Hello world|
+...
+```
+The third line above prints received data in hex format, that comes handy to display non printable data bytes.

examples/peripherals/uart_async_rxtxtasks/main/uart_async_rxtxtasks_main.c

@@ -61,6 +61,7 @@ static void rx_task()
         if (rxBytes > 0) {
             data[rxBytes] = 0;
             ESP_LOGI(RX_TASK_TAG, "Read %d bytes: '%s'", rxBytes, data);
+            ESP_LOG_BUFFER_HEXDUMP(RX_TASK_TAG, data, rxBytes, ESP_LOG_INFO);
         }
     }
     free(data);