Modify the BlinkThreadCallback example so you run two threads that blink different LEDs once per second by waiting for each other

Revision:
0:11ca69d691b7
Child:
1:30693312f670
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Nov 11 15:55:24 2018 +0000
@@ -0,0 +1,19 @@
+#include "mbed.h"
+
+Thread thread;
+DigitalOut led1(LED1);
+DigitalOut led2(LED2);
+
+// Blink function toggles the led in a long running loop
+void blink(DigitalOut *led) {
+    *led = !*led;
+    wait(1);
+}
+
+int main() {
+    while(true){
+        thread.start(callback(blink, &led1));
+        thread.join();
+        thread.start(callback(blink, &led2));
+    }
+}