Add an LED blinker sketch as an example for ESP32

blinker/blinker.ino

@@ -0,0 +1,10 @@
+const int LED_BUILTIN = 2;
+void setup() {
+    pinMode(LED_BUILTIN, OUTPUT);
+}
+void loop() {
+    digitalWrite(LED_BUILTIN, HIGH);
+    delay(1000);
+    digitalWrite(LED_BUILTIN, LOW);
+    delay(1000);
+}