fix: mitigate netlify javascript heap out of memory issue

docs/.vitepress/config.ts

@@ -5,6 +5,15 @@ import {
   localIconLoader
 } from 'vitepress-plugin-group-icons'
 
+let buildConcurrency: number
+try {
+  const { cpus } = await import('os')
+  buildConcurrency = 4 * cpus().length
+} catch {
+  // edge services may not expose os module
+  buildConcurrency = 16
+}
+
 export default defineConfig({
   title: 'VitePress',
 
@@ -15,6 +24,7 @@ export default defineConfig({
   lastUpdated: true,
   cleanUrls: true,
   metaChunk: true,
+  buildConcurrency,
 
   markdown: {
     math: true,