Add uart echo program

echo.c

@@ -0,0 +1,15 @@
+#include <util/delay.h>
+#include "drivers/uart_tx.h"
+#include "drivers/uart_rx_async.h"
+#include "drivers/led.h"
+
+#include <avr/interrupt.h>
+#include <avr/io.h>
+
+void uart_process(uint8_t c) {
+	uart_putc(c);
+}
+
+int main(void) {
+	for(;;) {}
+}