docs: Update showcase.md (#1031)

Xinyang Yu

2024-03-24 85a737b4ee72fb4dba12e1aacbd87d1636cfc30e

 quartz/components/Header.tsx

@@ -1,6 +1,6 @@
import { QuartzComponentConstructor, QuartzComponentProps } from "./types"
import { QuartzComponent, QuartzComponentConstructor, QuartzComponentProps } from "./types"

function Header({ children }: QuartzComponentProps) {
const Header: QuartzComponent = ({ children }: QuartzComponentProps) => {
  return children.length > 0 ? <header>{children}</header> : null
}