added new pitch and notes helper function

[SebastianBoldt]

Description

Currently it is impossible to extract the correct notes and their respective octaves from a chord object for a specific inversion.

I tried to obtain the correct notes and pitches for a chord by mapping all the note classes, since it was the only property available in the chord object.
I used the following code:

chord.noteClasses.map {
    Note($0.letter, accidental: $0.accidental, octave: 0).pitch
}

Unfortunately, the noteClasses do not contain the octave information, making it impossible for me to obtain the correct pitches for a specific chord inversion.

Proposed Solution

I would like to be able to do something like this:

chord.pitches(octave: 1) // Return the correct pitches taking into account the inversion

chord.notes(octave: 1) // Return the correct notes taking into account the inversion

[SebastianBoldt]

🥳

[SebastianBoldt]

@aure I think we could also try to build something similar for Scales.
If we obtain the Notes via the noteSet and map them to pitches they also do have the wrong octave order.

lldb) po Key.init(root: .init(.D, accidental: .natural), scale: .major).noteSet.array
▿ 7 elements
  ▿ 0 : C♯4
    ▿ noteClass : C♯
      - letter : Tonic.Letter.C
      - accidental : ♯
    - octave : 4
  ▿ 1 : D4
    ▿ noteClass : D
      - letter : Tonic.Letter.D
      - accidental : 
    - octave : 4
  ▿ 2 : E4
    ▿ noteClass : E
      - letter : Tonic.Letter.E
      - accidental : 
    - octave : 4
  ▿ 3 : F♯4
    ▿ noteClass : F♯
      - letter : Tonic.Letter.F
      - accidental : ♯
    - octave : 4
  ▿ 4 : G4
    ▿ noteClass : G
      - letter : Tonic.Letter.G
      - accidental : 
    - octave : 4
  ▿ 5 : A4
    ▿ noteClass : A
      - letter : Tonic.Letter.A
      - accidental : 
    - octave : 4
  ▿ 6 : B4
    ▿ noteClass : B
      - letter : Tonic.Letter.B
      - accidental : 
    - octave : 4
    ```

[Matt54]

Did we solve issue #25 with merging this PR?

[SebastianBoldt]

Did we solve issue #25 by merging this PR?

@Matt54 Nope, we solved this one
#22

#25 is about Keys
#22 was about Chords