Mark 3 symbols as combining accents (#2218)

crates/typst/src/eval/symbol.rs

@@ -153,6 +153,9 @@ impl Symbol {
             '\u{030c}' | 'ˇ' => '\u{030c}',
             '\u{20d6}' | '←' => '\u{20d6}',
             '\u{20d7}' | '→' | '⟶' => '\u{20d7}',
+            '\u{20d0}' | '↼' => '\u{20d0}',
+            '\u{20d1}' | '⇀' => '\u{20d1}',
+            '\u{20e1}' | '↔' | '⟷' => '\u{20e1}',
             _ => return None,
         })
     }