Add PSRAM test example

Author: Heltec-Aaron-Lee

examples/ESP32/PSRAM_Test/PSRAM_Test.ino

@@ -0,0 +1,26 @@
+/* Heltec Automation ESP32 external PSRAM read/write example
+ *
+ * Must have external PSRAM connected.
+ * 
+ * HelTec AutoMation, Chengdu, China
+ * 成都惠利特自动化科技有限公司
+ * https://heltec.org
+ *
+ * this project also realess in GitHub:
+ * https://github.com/HelTecAutomation/Heltec_ESP32
+ */
+
+
+#include <Arduino.h>
+
+void setup() {
+  Serial.begin(115200);
+  
+  Serial.printf("Total heap: %d\r\n", ESP.getHeapSize());
+  Serial.printf("Free heap: %d\r\n", ESP.getFreeHeap());
+  Serial.printf("Total PSRAM: %d\r\n", ESP.getPsramSize());
+  byte* psdRamBuffer = (byte*)ps_malloc(4000000);
+  Serial.printf("Free PSRAM: %d\r\n", ESP.getFreePsram());
+}
+
+void loop() {}