perf: preload css to improve loading speed

Co-authored-by: Divyansh Singh <40380293+brc-dd@users.noreply.github.com>

src/node/build/render.ts

@@ -101,7 +101,7 @@ export async function renderPage(
     .join('\n    ')
 
   const stylesheetLink = cssChunk
-    ? `<link rel="stylesheet" href="${siteData.base}${cssChunk.fileName}">`
+    ? `<link rel="preload stylesheet" href="${siteData.base}${cssChunk.fileName}" as="style">`
     : ''
 
   const title: string = createTitle(siteData, pageData)