fix(svelte): use user viewport store for init viewport closes #4335 (#4338)

* fix(svelte): use user viewport store for init viewport closes #4335

* refactor(svelte): viewport init

* chore(svelte): changelog

packages/svelte/src/lib/container/Zoom/Zoom.svelte

@@ -8,7 +8,7 @@
 
   type $$Props = ZoomProps;
 
-  export let initialViewport: $$Props['initialViewport'];
+  export let initialViewport: $$Props['initialViewport'] = undefined;
   export let onMoveStart: $$Props['onMoveStart'] = undefined;
   export let onMove: $$Props['onMove'] = undefined;
   export let onMoveEnd: $$Props['onMoveEnd'] = undefined;

packages/svelte/src/lib/container/Zoom/types.ts

@@ -1,7 +1,7 @@
 import type { OnMoveStart, OnMove, OnMoveEnd, PanOnScrollMode, Viewport } from '@xyflow/system';
 
 export type ZoomProps = {
-  initialViewport: Viewport;
+  initialViewport?: Viewport;
   panOnScrollMode: PanOnScrollMode;
   onMove?: OnMove;
   onMoveStart?: OnMoveStart;