feat: Generate index.html within path directories

This commit modifies the build script to generate `index.html` files inside
directories corresponding to the defined paths in `links.json`.

Previously, HTML files were generated directly as `[path].html`. This change
ensures that URLs like `/foo` and `/foo/` both correctly resolve to
`/foo/index.html`, preventing 404 errors due to trailing slash inconsistencies.

Author: denny0223

build.js

@@ -37,7 +37,8 @@ links.forEach(({ paths, url, title, description }) => {
     <p>正在前往 <a href="${url}">${title}</a></p>
 </body>
 </html>`;
-        fs.writeFileSync(`${linkPath}.html`, htmlContent, "utf8");
+        fs.mkdirSync(linkPath, { recursive: true });
+        fs.writeFileSync(path.join(linkPath, "index.html"), htmlContent, "utf8");
     });
 });