migrate app settings page to composition API and typescript

src/core/timezone.ts

@@ -1,5 +1,18 @@
 import type { TypeAndName } from './base.ts';
 
+export interface TimezoneInfo {
+    readonly displayName: string;
+    readonly timezoneName: string;
+}
+
+export interface LocalizedTimezoneInfo {
+    readonly name: string;
+    readonly utcOffset: string;
+    readonly utcOffsetMinutes: number;
+    readonly displayName: string;
+    readonly displayNameWithUtcOffset: string;
+}
+
 export class TimezoneTypeForStatistics implements TypeAndName {
     public static readonly ApplicationTimezone = new TimezoneTypeForStatistics(0, 'Application Timezone');
     public static readonly TransactionTimezone = new TimezoneTypeForStatistics(1, 'Transaction Timezone');