LibMarkdown: Implement introspection of the document tree

Author: https://github.com/BenWiederhake
Commit: 24e7196158
Pull-request: https://github.com/SerenityOS/serenity/pull/10420
Reviewed-by: https://github.com/petelliott ✅

Userland/Libraries/LibMarkdown/Paragraph.cpp

@@ -6,6 +6,7 @@
 
 #include <AK/StringBuilder.h>
 #include <LibMarkdown/Paragraph.h>
+#include <LibMarkdown/Visitor.h>
 
 namespace Markdown {
 
@@ -34,4 +35,13 @@ String Paragraph::render_for_terminal(size_t) const
     return builder.build();
 }
 
+RecursionDecision Paragraph::walk(Visitor& visitor) const
+{
+    RecursionDecision rd = visitor.visit(*this);
+    if (rd != RecursionDecision::Recurse)
+        return rd;
+
+    return m_text.walk(visitor);
+}
+
 }