fix(ImpressionArea): fix return type of ImpressionArea (#256)

Author: seungrodotlee

src/components/ImpressionArea/ImpressionArea.tsx

@@ -50,7 +50,7 @@ type Props<Tag extends ElementType> = React.ComponentPropsWithoutRef<Tag> &
  */
 export const ImpressionArea = forwardRef(ImpressionAreaImpl) as <T extends ElementType = 'div'>(
   props: Props<T> & { ref?: Ref<Element<T>> }
-) => React.ReactNode;
+) => React.ReactElement;
 
 function ImpressionAreaImpl<T extends ElementType = 'div'>(
   { as, rootMargin, areaThreshold, timeThreshold, onImpressionStart, onImpressionEnd, ...props }: Props<T>,