fix: Change scrollable parent check depending on the config.shadowDom property (fixes #940)

Author: Jasenkoo

src/VueDatePicker/composables/position.ts

@@ -233,7 +233,8 @@ export const usePosition = ({
     const getScrollableParent = function (el: HTMLElement | null): Window | HTMLElement {
         if (!el || el === document.body || el.nodeType === Node.DOCUMENT_FRAGMENT_NODE) return window;
         if (isScrollable(el)) return el;
-        return getScrollableParent((el.assignedSlot ? el.assignedSlot.parentNode : el.parentNode) as HTMLElement);
+        const parent = defaultedConfig.value.shadowDom ? 'parentNode' : 'parentElement';
+        return getScrollableParent((el.assignedSlot ? el.assignedSlot[parent] : el[parent]) as HTMLElement);
     };
 
     const getShadowPos = (rect?: DOMRect) => {