ast: add continue expression

src/ast.rs

@@ -354,6 +354,7 @@ impl<A: Annotation> Display for Expr<A> {
             Self::Bind(v) => v.fmt(f),
             Self::Make(v) => v.fmt(f),
 
+            Self::Op(op @ Op::Continue, exprs) => f.delimit(op, "").list(exprs, "!?,"),
             Self::Op(op @ (Op::If | Op::While), exprs) => match exprs.as_slice() {
                 [cond, pass, Anno(Expr::Op(Op::Tuple, e), _)] if e.is_empty() => {
                     write!(f, "{op}{cond} {pass}")