fix(div): update class name to remove weird space afterwards (#763)

Signed-off-by: Aaron <29749331+aarnphm@users.noreply.github.com>

quartz/components/Spacer.tsx

@@ -1,7 +1,8 @@
 import { QuartzComponentConstructor, QuartzComponentProps } from "./types"
+import { classNames } from "../util/lang"
 
 function Spacer({ displayClass }: QuartzComponentProps) {
-  return <div class={`spacer ${displayClass ?? ""}`}></div>
+  return <div class={classNames(displayClass, "spacer")}></div>
 }
 
 export default (() => Spacer) satisfies QuartzComponentConstructor