Add await_ready.cpp example

rt/examples/await_ready.cpp

+#include <typon/typon.hpp>
+
+using namespace typon;
+
+int fibo(int n) {
+  if (n < 2)
+    return n;
+  return fibo(n - 1) + fibo(n - 2);
+}
+
+Task<int> fibo_task(int n) {
+  int r = co_await fibo(n);
+  co_return r;
+}
+
+Join<int> fibo_join(int n) {
+  if (n < 8) {
+    int x = co_await fibo(n - 1);
+    int y = co_await fibo_task(n - 2);
+    co_return x + y;
+  }
+  Forked a = co_await fork(fibo_join(n - 1));
+  int b = co_await fibo_join(n - 2);
+  co_await Sync();
+  co_return a.get() + b;
+}
+
+Root root() {
+  int result = co_await fibo_join(40);
+  printf("%d\n", result);
+}
+
+int main() {
+  root().call();
+  return 0;
+}