Update temperature.py

Add some comments from the RP2040 datasheet that helps new users understand where the constant number values came from.

adc/temperature.py

@@ -7,6 +7,8 @@ conversion_factor = 3.3 / (65535)
 while True:
     reading = sensor_temp.read_u16() * conversion_factor
     
+    # The temperature sensor measures the Vbe voltage of a biased bipolar diode, connected to the fifth ADC channel
+    # Typically, Vbe = 0.706V at 27 degrees C, with a slope of -1.721mV (0.001721) per degree. 
     temperature = 27 - (reading - 0.706)/0.001721
     print(temperature)
     utime.sleep(2)