feat: add SynchronousQueueDemo demonstrating direct handoff between producer and consumer threads

Implemented SynchronousQueueDemo.java to illustrate how SynchronousQueue enables
thread-to-thread data exchange without internal capacity. Demonstrates blocking
behavior where put() waits for take(), ensuring synchronized handoff and zero buffering.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan