feat: support unicode mult & div

src/nodes/from_str.rs

@@ -21,8 +21,8 @@ impl TryFrom<char> for Operator {
         match value {
             '+' => Ok(Self::Plus),
             '-' => Ok(Self::Minus),
-            '*' => Ok(Self::Mult),
-            '/' => Ok(Self::Div),
+            '*' | '×' => Ok(Self::Mult),
+            '/' | '÷' => Ok(Self::Div),
             '^' => Ok(Self::Exp),
             _ => Err(value),
         }