Fix: Make CalendarIconProps.icon optional

- Changed CalendarIconProps.icon from required to optional
- Updated related types to avoid breaking changes
- Ensured backward compatibility

Using React 18.3.1, the 'icon' property obtained via Pick became required, causing a type error.
To prevent this issue, I explicitly marked 'icon' as optional by using Partial.

Author: jingjing2222

src/index.tsx

@@ -125,7 +125,7 @@ export type DatePickerProps = OmitUnion<
   | "selectsMultiple"
   | "dropdownMode"
 > &
-  Pick<CalendarIconProps, "icon"> &
+  Partial<Pick<CalendarIconProps, "icon">> &
   OmitUnion<PortalProps, "children" | "portalId"> &
   OmitUnion<
     PopperComponentProps,