chore: import upstream snapshot with attribution

apps/docs/app/sitemap.ts

@@ -0,0 +1,42 @@
+import type { MetadataRoute } from 'next'
+import { i18n } from '@/lib/i18n'
+import { source } from '@/lib/source'
+import { DOCS_BASE_URL } from '@/lib/urls'
+
+export const revalidate = 3600
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  const baseUrl = DOCS_BASE_URL
+  const languages = source.getLanguages()
+
+  const pagesBySlug = new Map<string, Map<string, string>>()
+  for (const { language, pages } of languages) {
+    for (const page of pages) {
+      const key = page.slugs.join('/')
+      if (!pagesBySlug.has(key)) {
+        pagesBySlug.set(key, new Map())
+      }
+      pagesBySlug.get(key)!.set(language, `${baseUrl}${page.url}`)
+    }
+  }
+
+  const entries: MetadataRoute.Sitemap = []
+  for (const [, localeMap] of pagesBySlug) {
+    const defaultUrl = localeMap.get(i18n.defaultLanguage)
+    if (!defaultUrl) continue
+
+    const langAlternates: Record<string, string> = {}
+    for (const [lang, url] of localeMap) {
+      langAlternates[lang] = url
+    }
+
+    langAlternates['x-default'] = defaultUrl
+
+    entries.push({
+      url: defaultUrl,
+      alternates: { languages: langAlternates },
+    })
+  }
+
+  return entries
+}