Adds rfid example code.

device/main/RFIDInterface.cpp

@@ -0,0 +1,26 @@
+#include "RFIDInterface.hpp"
+
+#include <esp_log.h>
+
+static const char* TAG = "rfid";
+
+void tag_handler(uint8_t* sn) { // serial number is always 5 bytes long
+    ESP_LOGI(TAG, "Tag: %#x %#x %#x %#x %#x",
+        sn[0], sn[1], sn[2], sn[3], sn[4]
+    );
+}
+
+RFIDInterface::RFIDInterface() {
+	startConfig = (rc522_start_args_t){
+        .miso_io     = 26,
+        .mosi_io     = 25,
+		.sck_io      = 23,
+        .sda_io      = 5,
+        .callback    = &tag_handler
+	};
+}
+
+void RFIDInterface::start() {
+	rc522_start(startConfig);
+}
+