Add Blink sketch

Week 4/Blink/Blink.ino

@@ -0,0 +1,14 @@
+#define LED_BUILTIN D4
+
+void setup() {
+  pinMode(LED_BUILTIN,OUTPUT);
+
+}
+
+void loop() {
+  digitalWrite(LED_BUILTIN,LOW);
+  delay(1000);
+
+  digitalWrite(LED_BUILTIN,HIGH);
+  delay(1000);
+}