fix(trackerEntryModel): switch from class to interface

src/models/TrackerEntry.ts

@@ -1,11 +1,4 @@
-class TrackerEntry {
+export default interface TrackerEntry {
   date: string;
   quantity: number;
-
-  constructor({ date, quantity }: TrackerEntry) {
-    this.date = date;
-    this.quantity = quantity;
-  }
 }
-
-export default TrackerEntry;