Add speaker in readme for pico_tone

Author: jcarranz97

README.md

@@ -244,7 +244,7 @@ App|Description
 [hello_pwm](pwm/hello_pwm) | Minimal example of driving PWM output on GPIOs.
 [led_fade](pwm/led_fade) | Fade an LED between low and high brightness. An interrupt handler updates the PWM slice's output level each time the counter wraps.
 [measure_duty_cycle](pwm/measure_duty_cycle) | Drives a PWM output at a range of duty cycles, and uses another PWM slice in input mode to measure the duty cycle.
-[pico_tone](pwm/pico_tone) | Play a christmas melody :notes::christmas_tree: by generating square waves with PWM and a Buzzer.
+[pico_tone](pwm/pico_tone) | Play a christmas melody :notes::christmas_tree: by generating square waves with PWM and a Buzzer :speaker:.
 
 ### Reset