Migrate to app router (#2254)

components/HeadingAnchor/HeadingAnchor.tsx

@@ -9,7 +9,14 @@ export type HeadingAnchorProps = Omit<ComponentPropsWithoutRef<typeof Link>, "hr
 
 const HeadingAnchor = ({ id, title, ...rest }: HeadingAnchorProps) => {
   return (
-    <Link href={`#${id}`} title={`Jump to "${title}"`} aria-hidden underline={false} css={{ lineHeight: 1 }} {...rest}>
+    <Link
+      href={`#${id}`}
+      title={`Jump to "${title}"`}
+      aria-hidden
+      underline={false}
+      style={{ lineHeight: 1 }}
+      {...rest}
+    >
       <FiLink size="0.8em" />
     </Link>
   );