fix: copy index.html to 404.html for GitHub Pages

Author: evermake

package.json

@@ -6,7 +6,7 @@
   "packageManager": "pnpm@10.25.0",
   "scripts": {
     "dev": "vite",
-    "build": "tsc -b && vite build",
+    "build": "tsc -b && vite build && cp ./dist/index.html ./dist/404.html",
     "lint": "eslint .",
     "preview": "vite preview"
   },