LibMarkdown: Add additional spacing for terminal rendering

This patch adds spacing to give a sense of structure to markdown
documents viewed in the terminal. This also makes the content easier
to read.

Userland/Libraries/LibMarkdown/Table.cpp

@@ -63,6 +63,8 @@ String Table::render_for_terminal(size_t view_width) const
         builder.append("\n");
     }
 
+    builder.append("\n");
+
     return builder.to_string();
 }