Implement equality operator for indicator state change class

Author: Kamil Klyta

lib/src/data/indicator_state_change.dart

@@ -21,6 +21,16 @@ class IndicatorStateChange {
     return currentState == from && newState == to;
   }
 
+  @override
+  bool operator ==(Object other) =>
+      other.runtimeType == runtimeType &&
+      other is IndicatorStateChange &&
+      other.currentState == currentState &&
+      other.newState == newState;
+
+  @override
+  int get hashCode => Object.hash(currentState, newState);
+
   @override
   String toString() =>
       "$runtimeType(${describeEnum(currentState)} → ${describeEnum(newState)})";