feat: support subscript and superscript

examples/html-slugify.rs

@@ -50,7 +50,7 @@ impl Traverser for MyHtmlHandler {
         special_block quote_block center_block verse_block comment_block example_block export_block
         source_block babel_call clock cookie radio_target drawer dyn_block fn_def fn_ref macros
         snippet timestamp target fixed_width org_table org_table_row org_table_cell latex_fragment
-        latex_environment entity line_break
+        latex_environment entity line_break superscript subscript
     }
 }