chore: fix typo

lib/generate-rss.js

@@ -7,7 +7,7 @@ const generateRssItem = (post) => `
     <guid>${siteMetadata.siteUrl}/blog/${post.slug}</guid>
     <title>${escape(post.title)}</title>
     <link>${siteMetadata.siteUrl}/blog/${post.slug}</link>
-    ${post.summary && <description>escape(post.summary)</description>}
+    ${post.summary && `<description>${escape(post.summary)}</description>`}
     <pubDate>${new Date(post.date).toUTCString()}</pubDate>
     <author>${siteMetadata.email} (${siteMetadata.author})</author>
     ${post.tags && post.tags.map((t) => `<category>${t}</category>`).join('')}