fix: Fix Backlinks not applying the display class (#519)

* fix: Fix `Backlinks` not applying the display class

Fix #518

* fix: Apply `displayClass` to all layout components

* refactor: Use same style

* fix: Remove `undefined` class using coalescing operator

quartz/components/Darkmode.tsx

@@ -3,11 +3,11 @@
 // see: https://v8.dev/features/modules#defer
 import darkmodeScript from "./scripts/darkmode.inline"
 import styles from "./styles/darkmode.scss"
-import { QuartzComponentConstructor } from "./types"
+import { QuartzComponentConstructor, QuartzComponentProps } from "./types"
 
-function Darkmode() {
+function Darkmode({ displayClass }: QuartzComponentProps) {
   return (
-    <div class="darkmode">
+    <div class={`darkmode ${displayClass ?? ""}`}>
       <input class="toggle" id="darkmode-toggle" type="checkbox" tabIndex={-1} />
       <label id="toggle-label-light" for="darkmode-toggle" tabIndex={-1}>
         <svg