update ChangeFreq to support typescript configurations with string literal (withastro#6262)

* update `ChangeFreq`

* `pnpm exec changeset`

* use @Princesseuh suggested change

* Revert "use @Princesseuh suggested change"

This reverts commit a1e5660.

* use @Princesseuh suggested change and an `as`

Author: vic1707

.changeset/shiny-years-beg.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/sitemap': minor
+---
+
+update `ChangeFreq` to support typescript configurations with string literal or predefined value.

packages/integrations/sitemap/src/generate-sitemap.ts

@@ -1,3 +1,4 @@
+import { EnumChangefreq } from 'sitemap';
 import type { SitemapItem, SitemapOptions } from './index.js';
 import { parseUrl } from './utils/parse-url.js';
 
@@ -44,7 +45,7 @@ export function generateSitemap(pages: string[], finalSiteUrl: string, opts: Sit
 			links,
 			lastmod,
 			priority,
-			changefreq,
+			changefreq: changefreq as EnumChangefreq,
 		};
 	});
 

packages/integrations/sitemap/src/index.ts

@@ -12,7 +12,7 @@ import { generateSitemap } from './generate-sitemap.js';
 import { Logger } from './utils/logger.js';
 import { validateOptions } from './validate-options.js';
 
-export type ChangeFreq = EnumChangefreq;
+export type ChangeFreq = `${EnumChangefreq}`;
 export type SitemapItem = Pick<
 	SitemapItemLoose,
 	'url' | 'lastmod' | 'changefreq' | 'priority' | 'links'