BLOG-14 Create not found page (#23)

### Description

- Add Not Found Page
- Change the home page h1 font weight
- Change the order of Prettier plugins to fix the issue of tailwind css not being sorted

### Package Changes

_No response_

### Screenshots

| Desktop (FHD 1920x1080) | Mobile (iPhone16 Pro 390x844) |
| --- | --- |
| ![image.png](/attachments/d3863cb9-f834-4c42-a45e-c08feacdbe0f) | <img src="/attachments/6d3f21fe-a01b-4f02-86e1-9f917345e796" width="400" /> |

### Reference

Resolves #14

### Checklist

- [x] A milestone is set

Reviewed-on: #23
Reviewed-by: squid <squid@squidspirit.com>
Co-authored-by: Zoe <7711zoe@gmail.com>
Co-committed-by: Zoe <7711zoe@gmail.com>

frontend/.prettierrc

@@ -1,5 +1,5 @@
 {
-  "plugins": ["prettier-plugin-tailwindcss", "@trivago/prettier-plugin-sort-imports"],
+  "plugins": ["@trivago/prettier-plugin-sort-imports", "prettier-plugin-tailwindcss"],
   "printWidth": 120,
   "tabWidth": 2,
   "trailingComma": "all",

frontend/src/app/not-found.tsx

@@ -0,0 +1,16 @@
+export default function NotFoundPage() {
+  return (
+    <div className="mx-auto flex min-h-[--content-height] max-w-screen-xl flex-col items-center justify-center px-4 md:px-6">
+      <div className="flex flex-row items-end gap-x-4 md:gap-x-6">
+        <h1 className="text-5xl font-extrabold text-gray-800 underline md:text-7xl">404</h1>
+        <h2 className="flex flex-row items-center gap-x-2 text-2xl font-bold md:gap-x-2.5 md:text-3xl">
+          <div className="h-7 w-1.5 bg-gray-800 md:h-9 md:w-2" />
+          <div className="rounded-md bg-blue-600 px-1 py-px md:px-1.5 md:py-0.5">
+            <span className="text-white">Not</span>
+          </div>
+          <span className="text-gray-800">Found.</span>
+        </h2>
+      </div>
+    </div>
+  );
+}

frontend/src/app/page.tsx

@@ -4,7 +4,7 @@ export default function HomePage() {
   return (
     <div className="mx-auto flex min-h-[--content-height] max-w-screen-xl flex-col justify-center gap-y-2.5 px-4 md:gap-y-8 md:px-6">
       <h2 className="text-3xl font-bold text-gray-800 md:text-6xl">Hello 大家好！</h2>
-      <h1 className="flex flex-row items-center gap-x-2 text-4xl font-bold text-gray-800 md:text-7xl">
+      <h1 className="flex flex-row items-center gap-x-2 text-4xl font-extrabold text-gray-800 md:text-7xl">
         <span>我是</span>
         <div className="rounded-lg bg-blue-600 px-1.5 py-1">
           <span className="text-white">Squid</span>