Update documentation

Author: sebromero

docs/api.md

@@ -120,10 +120,7 @@ Predefined notes are available in the NOTES dictionary e.g. ModulinoBuzzer.NOTES
 
 Dictionary with the notes and their corresponding frequencies.
 The supported notes are defined as follows:
-- B0
-- C1, CS1, D1, DS1, E1, F1, FS1, G1, GS1, A1, AS1, B1
-- C2, CS2, D2, DS2, E2, F2, FS2, G2, GS2, A2, AS2, B2
-- C3, CS3, D3, DS3, E3, F3, FS3, G3, GS3, A3, AS3, B3
+- FS3, G3, GS3, A3, AS3, B3
 - C4, CS4, D4, DS4, E4, F4, FS4, G4, GS4, A4, AS4, B4
 - C5, CS5, D5, DS5, E5, F5, FS5, G5, GS5, A5, AS5, B5
 - C6, CS6, D6, DS6, E6, F6, FS6, G6, GS6, A6, AS6, B6
@@ -161,7 +158,7 @@ If blocking is set to True, the function will wait until the tone is finished.
 
 **Arguments**:
 
-- `frequency` - The frequency of the tone in Hz
+- `frequency` - The frequency of the tone in Hz (freuqencies below 180 Hz are not supported)
 - `lenght_ms` - The duration of the tone in milliseconds. If omitted, the tone will play indefinitely
 - `blocking` - If set to True, the function will wait until the tone is finished