Added more sweeping conformances to Sendable and Hashable; made "shortcuts" concurrency-safe (#56)

* Update Chord.swift

Added `Hashable` conformance to `Chord`.

* Update Key.swift

Added `Hashable` conformance to `Key`.

* Update Accidental.swift

Added `Sendable` conformance to `Accidental`.

* Update Letter.swift

Added `Sendable` conformance to `Letter`.

* Update NoteClass.swift

Added `Sendable` conformance to `NoteClass`.

* Update ChordType.swift

Added `Sendable` conformance to `ChordType`.

* Update Chord.swift

Added `Sendable` conformance to `Chord`.

* Update Interval.swift

Added `Sendable` conformance to `Interval`.

* Update Scale.swift

Added `Sendable` conformance to `Scale`.

* Update BitSet.swift

Added `Sendable` conformance to `BitSet` protocol.

* Update BitSet.swift

Added `Sendable` conformance to `BitSetAdapter`.

* Update Key.swift

Added `Sendable` conformance to `Key`.

* Update Note.swift

Added `Sendable` conformance to `Note`.

* Update Note+MiddleCStandard.swift

Added `Sendable` conformance to `Note.MiddleCStandard`.

* Update Octave.swift

Added `Sendable` conformance to `Octave`.

* Update Pitch.swift

Added `Sendable` conformance to `Pitch`.

* Update PitchColor.swift

Added `Sendable` conformance to `PitchColor`.

* Update NoteClass+Shortcuts.swift

Changed static variable to static constant, as it shouldn't be mutable.

* Update NoteClass+Shortcuts.swift

Changed remaining `NoteClass` static variable "shortcuts" to static constants. This ensures that they're concurrency-safe. They shouldn't be mutable anyway.

* Update Chord+Shortcuts.swift

Changed remaining `Chord` static variable "shortcuts" to static constants. This ensures that they're concurrency-safe. They shouldn't be mutable anyway.

* Update Note+Shortcuts.swift

Changed remaining `Note` static variable "shortcuts" to static constants. This ensures that they're concurrency-safe. They shouldn't be mutable anyway.

Author: edonv

Sources/Tonic/Accidental.swift

@@ -5,7 +5,7 @@ import Foundation
 /// A way to describe modification to a ``Note`` or ``NoteClass``
 ///
 /// A semitone offset applied to a note that does not change the letter of the note, just the pitch.
-public enum Accidental: Int8, CaseIterable, Equatable, Hashable, Codable {
+public enum Accidental: Int8, Sendable, CaseIterable, Equatable, Hashable, Codable {
     static var count: Int { Accidental.allCases.count }
     static var naturalIndex: Int { count / 2 }
 

Sources/Tonic/BitSet.swift

@@ -3,7 +3,7 @@
 import Foundation
 
 /// Interface to bit sets used to represent sets of pitches and sets of notes.
-public protocol BitSet: Hashable, Codable {
+public protocol BitSet: Hashable, Codable, Sendable {
     init()
     func isSet(bit: Int) -> Bool
     mutating func add(bit: Int)
@@ -195,7 +195,7 @@ public protocol IntRepresentable {
     var intValue: Int { get }
 }
 
-public struct BitSetAdapter<T: IntRepresentable, B: BitSet>: Hashable, Codable {
+public struct BitSetAdapter<T: IntRepresentable, B: BitSet>: Sendable, Hashable, Codable {
     public var bits: B
 
     public init() {