docs(en): add docs for including RSS post content

src/pages/en/guides/rss.md

@@ -114,6 +114,33 @@ export const get = () => rss({
 });
 ```
 
+### Including full post content
+
+By default, the Astro RSS integration does not support including the content of each of your posts in the feed itself. 
+
+However, if you create the list of RSS feed objects yourself, you can pass the content of Markdown files (not MDX), to the `content` key using the [`compiledContent` property](/en/guides/markdown-content/#exported-properties). We suggest using a package like [`sanitize-html`](https://www.npmjs.com/package/sanitize-html) in order to make sure that your content is properly sanitized, escaped, and encoded for use in the XML feed.
+
+```js ins={2, 15} title={src/pages/rss.xml.js}
+import rss from '@astrojs/rss';
+import sanitizeHtml from 'sanitize-html';
+
+// Works with Markdown files only!
+const postImportResult = import.meta.glob('../posts/**/*.md', { eager: true }); 
+const posts = Object.values(postImportResult);
+
+export const get = () => rss({
+  title: 'Buzz’s Blog',
+  description: 'A humble Astronaut’s guide to the stars',
+  site: import.meta.env.SITE,
+  items: posts.map((post) => ({
+    link: post.url,
+    title: post.frontmatter.title,
+    pubDate: post.frontmatter.pubDate,
+    content: sanitizeHtml(post.compiledContent()),
+  }))
+});
+```
+
 ## Adding a stylesheet
 
 You can style your RSS feed for a more pleasant user experience when viewing the file in your browser.