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/ContentMeta.tsx

@@ -3,7 +3,7 @@ import { QuartzComponentConstructor, QuartzComponentProps } from "./types"
 import readingTime from "reading-time"
 
 export default (() => {
-  function ContentMetadata({ cfg, fileData }: QuartzComponentProps) {
+  function ContentMetadata({ cfg, fileData, displayClass }: QuartzComponentProps) {
     const text = fileData.text
     if (text) {
       const segments: string[] = []
@@ -14,7 +14,7 @@ export default (() => {
       }
 
       segments.push(timeTaken)
-      return <p class="content-meta">{segments.join(", ")}</p>
+      return <p class={`content-meta ${displayClass ?? ""}`}>{segments.join(", ")}</p>
     } else {
       return null
     }