feat: added custom 404 page

Author: steadyfall

src/app/not-found.tsx

@@ -0,0 +1,27 @@
+import BackButton from "@/components/ui/BackButton";
+import { cn } from "@/lib/utils";
+
+export default function NotFound() {
+    return (
+    <main className="flex flex-col items-center container mt-[28vh] z-1">
+        <h1 className={
+            cn(
+                "font-typewriter text-6xl md:text-7xl lg:text-8xl font-bold",
+                "text-transparent bg-clip-text bg-gradient-to-r dark:from-gray-500 dark:to-gray-300 from-gray-500 to-gray-700"
+            )
+        }>
+            404
+        </h1>
+        <div className="mt-4 text-center">
+            The page you're looking for, is either not there or has been moved.
+        </div>
+        <ul className="mt-4 flex gap-4 sm:gap-8">
+            <li>{<BackButton>go back</BackButton>}</li>
+            <li>|</li>
+            <li><a href="/" className="text-slate-600 dark:text-slate-300 hover:text-black dark:hover:text-white hover:underline hover:underline-offset-4">home</a></li>
+        </ul>
+    </main>
+    )
+}
+
+