perf: render pages asynchronously (#1320)

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

src/node/build/build.ts

@@ -65,8 +65,9 @@ export async function build(
 
       const pages = ['404.md', ...siteConfig.pages]
 
-      for (const page of pages) {
+      await Promise.all(
-        await renderPage(
+        pages.map((page) =>
+          renderPage(
             render,
             siteConfig,
             page,
@@ -76,7 +77,8 @@ export async function build(
             pageToHashMap,
             hashMapString
           )
-      }
+        )
+      )
     } catch (e) {
       spinner.stopAndPersist({
         symbol: failMark