Added package initializers to the Amiibo models for testing.

Sources/AmiiboService/Public/Models/GameCharacter.swift

@@ -25,6 +25,12 @@ public struct GameCharacter: KeyNameModel {
     
     // MARK: Initializers
 
+    /// Initializes this model.
+    package init(key: String, name: String) {
+        self.key = key
+        self.name = name
+    }
+
     /// Initializes this model from a given payload.
     /// - Parameter payload: A payload that contains the values for the model.
     init(_ payload: some KeyNamePayload) {