[TASK] apply sticky to first two summary headlines

src/main.rs

@@ -57,7 +57,7 @@ fn print_header(header: Heading, level: usize) -> String {
 
     ret.push_str(&format!(
         "<details>\
-            <summary><h{0}>{1}</h{0}></summary>\n\
+            <summary class='sticky'><h{0}>{1}</h{0}></summary>\n\
             <div>",
         level + 2,
         header_title