ESP32 HC-SR04 Ultrasonic Distance Sensor

The HC-SR04 ultrasonic sensor calculates distance by measuring the time it takes for the sound wave it emits to bounce off an object and return (Time of Flight). In this project, we will send a 10-microsecond pulse to the TRIG pin of the ESP32 and read the echo duration from the ECHO pin using `pulseIn()`. We will display the calculated distance in centimeters on the Serial Monitor. Since the HC-SR04 operates at 5V, a **voltage divider** is required on the ECHO pin—otherwise, the ESP32’s 3.3V GP