fix(daterangepicker): modify the characterprop to be optional (#1518)

Modify the `character`prop to be optional on DateRangePicker

Author: simonguo

src/DateRangePicker/DateRangePicker.tsx

@@ -83,7 +83,7 @@ export interface DateRangePickerProps extends PickerBaseProps, FormControlBasePr
   defaultCalendarValue?: ValueType;
 
   /** The character that separates two dates */
-  character: string;
+  character?: string;
 
   /** Disabled date */
   disabledDate?: DisabledDateFunction;