Add Uno R4 WiFi support to examples

[ShortArrow]

Expected

Need const like UNO_R4_WIFI.
And include WiFiS3.h.

Note: this is tested by my Uno R4 WiFi.

#include <ArduinoMqttClient.h>
#include <WiFiS3.h>
#include "arduino_secrets.h"

Actual

ArduinoMqttClient/examples/WiFiSimpleReceive/WiFiSimpleReceive.ino

Lines 14 to 22 in 107090e

	#if defined(ARDUINO_SAMD_MKRWIFI1010) || defined(ARDUINO_SAMD_NANO_33_IOT) || defined(ARDUINO_AVR_UNO_WIFI_REV2)
	#include <WiFiNINA.h>
	#elif defined(ARDUINO_SAMD_MKR1000)
	#include <WiFi101.h>
	#elif defined(ARDUINO_ARCH_ESP8266)
	#include <ESP8266WiFi.h>
	#elif defined(ARDUINO_PORTENTA_H7_M7) || defined(ARDUINO_NICLA_VISION) || defined(ARDUINO_ARCH_ESP32) || defined(ARDUINO_GIGA)
	#include <WiFi.h>
	#endif

ArduinoMqttClient/examples/WiFiSimpleSender/WiFiSimpleSender.ino

Lines 14 to 22 in 107090e

	#if defined(ARDUINO_SAMD_MKRWIFI1010) || defined(ARDUINO_SAMD_NANO_33_IOT) || defined(ARDUINO_AVR_UNO_WIFI_REV2)
	#include <WiFiNINA.h>
	#elif defined(ARDUINO_SAMD_MKR1000)
	#include <WiFi101.h>
	#elif defined(ARDUINO_ARCH_ESP8266)
	#include <ESP8266WiFi.h>
	#elif defined(ARDUINO_PORTENTA_H7_M7) || defined(ARDUINO_NICLA_VISION) || defined(ARDUINO_ARCH_ESP32) || defined(ARDUINO_GIGA)
	#include <WiFi.h>
	#endif

[jwilleke]

Works for me with

#include <ArduinoMqttClient.h>
#include <SPI.h>
#include <PubSubClient.h>
#include "WiFi.h"
#include <WiFiClient.h>