Add support for 16 Holes C Chromatic Harmonica Standard Tuning.

[Ismael-VC]

• I have updated the README, to reflect what the plugin actually does.
• Added support for the 16 hole chromatic harp.
• fixed a bug with tabbing the D7 note in standard chromatic:

// C7,   C#7,    D7  < ---this is wrong, should be "-12s" not "-12" which corresponds to B6 not D7!     
"+12", "+12s", "-12", "-12s" ]; 

[Ismael-VC]

@vpereverzev @Ximich sorry to bother you, since you are the only ones in the musescore organization I would like to request if you can please check this out, else may I join this repo as contributor? I could check out all the other PR and issues and take maintenance of this plugin.

Best regards.