Add fix for comrak bug not finding frontmatter

src/models/challenge.rs

@@ -31,8 +31,11 @@ impl Challenge {
         let arena = Arena::new();
         let root = parse_document(
             &arena,
-            &fs::read_to_string(format!("content/challenges/{number}.md"))
+           & (fs::read_to_string(format!("content/challenges/{number}.md"))
-                .expect("Couldn't find challenge file"),
+                .expect("Couldn't find challenge file")
+                // comrak can't find frontmatter if there's only frontmatter and no newline at end
+                // TODO: Open issue in comrak
+                + "\n"),
             &options,
         );
         if let Some(node) = root.children().next() {