Add implementation of shuffle on IdentifiedArray (#254)

* add shuffle

* Update Tests/ComposableArchitectureTests/IdentifiedArrayTests.swift

* Update IdentifiedArrayTests.swift

Co-authored-by: Stephen Celis <stephen.celis@gmail.com>

Sources/ComposableArchitecture/SwiftUI/IdentifiedArray.swift

@@ -190,6 +190,15 @@ where ID: Hashable {
       try areInIncreasingOrder(self.dictionary[$0]!, self.dictionary[$1]!)
     }
   }
+  
+  public mutating func shuffle<T>(using generator: inout T) where T : RandomNumberGenerator {
+    ids.shuffle(using: &generator)
+  }
+  
+  public mutating func shuffle() {
+    var rng = SystemRandomNumberGenerator()
+    self.shuffle(using: &rng)
+  }
 }
 
 extension IdentifiedArray: CustomDebugStringConvertible {