fix: date-time widget coercition

Author: JulianCataldo

packages/shoelace/src/widgets/date.ts

@@ -16,8 +16,12 @@ export const date: Widgets['date'] = (options) => html`
 .id=${options.id}
 .required=${options.required ?? false}
 @sl-input=${(event: CustomEvent) => {
-const { valueAsDate: newValue } = event.target as SlInput;
-options.valueChangedCallback?.(newValue ?? undefined);
+const { valueAsDate: newValue, value } = event.target as SlInput;
+
+options.valueChangedCallback?.(
+// NOTE: Date time does not return `valueAsDate`
+newValue ?? value ? new Date(value) : undefined,
+);
 }}
 >
 </sl-input>