Add last date for storage

TempTrack/Storage/TemperatureStorage.swift

@@ -11,6 +11,18 @@ final class TemperatureStorage: ObservableObject {
         in: .userDomainMask,
         appropriateFor: nil, create: true)
     }
+    
+    @AppStorage("newestDate")
+    private var newestMeasurementTime: Int = 0
+    
+    private var newestMeasurementDate: Date {
+        get {
+            Date(seconds: newestMeasurementTime)
+        }
+        set {
+            newestMeasurementTime = newValue.seconds
+        }
+    }
 
     @Published
     var recentMeasurements: [TemperatureMeasurement]