feat: add RSS xml (#34)

* feat: add RSS xml

---------

Co-authored-by: saicaca <zephyird@gmail.com>

src/pages/rss.xml.ts

@@ -0,0 +1,25 @@
+import rss from '@astrojs/rss';
+import {siteConfig} from '@/config';
+import { getCollection } from 'astro:content';
+import sanitizeHtml from 'sanitize-html';
+import MarkdownIt from 'markdown-it';
+const parser = new MarkdownIt();
+
+export async function GET(context: any) {
+  const blog = await getCollection('posts');
+  return rss({
+    title: siteConfig.title,
+    description: siteConfig.subtitle || 'No description',
+    site: context.site,
+    items: blog.map((post) => ({
+        title: post.data.title,
+        pubDate: post.data.published,
+        description: post.data.description,
+        link: `/posts/${post.slug}/`,
+        content: sanitizeHtml(parser.render(post.body), {
+          allowedTags: sanitizeHtml.defaults.allowedTags.concat(['img'])
+        }),
+      })),
+    customData: `<language>${siteConfig.lang}</language>`,
+  });
+}