feat(sitemap): add configurable XML namespaces support

src/content/docs/en/guides/integrations-guide/sitemap.mdx

@@ -475,6 +475,33 @@ export default defineConfig({
 
 The given configuration will generate sitemap files at `https://example.com/astronomy-sitemap-0.xml` and `https://example.com/astronomy-sitemap-index.xml`.
 
+### `namespaces`
+
+**Type:** `{ news?: boolean; xhtml?: boolean; image?: boolean; video?: boolean; }`  
+**Default:** `{ news: true, xhtml: true, image: true, video: true }`
+
+Controls which XML namespaces are included in the sitemap generation.
+
+By default, all namespaces default to `true` and you must explicitly set each one you want to change to `false`.
+
+```js title="astro.config.mjs" ins={8-14}
+import { defineConfig } from 'astro/config';
+import sitemap from '@astrojs/sitemap';
+
+export default defineConfig({
+  site: 'https://example.com',
+  integrations: [
+    sitemap({
+      // Only include image and video namespaces
+      namespaces: {
+        news: false,
+        xhtml: false, 
+        // image and video will be true by default
+      }
+    })
+  ]
+});
+
 ## Examples
 
 * The official Astro website uses Astro Sitemap to generate [its sitemap](https://astro.build/sitemap-index.xml).