Add support for variadic arguments in WebIDL

crates/webidl-tests/simple.rs

@@ -90,6 +90,12 @@ fn optional_and_union_arguments() {
     assert_eq!(f.m_with_b_and_str_and_opt_bool("abc", false, "5", Some(true)), "string, abc, boolean, false, string, 5, boolean, true");
 }
 
+#[wasm_bindgen_test]
+fn variadic() {
+    let f = Variadic::new().unwrap();
+    assert_eq!(f.sum(Box::new([1, 2, 3, 4, 5])), 15);
+}
+
 #[wasm_bindgen_test]
 fn unforgeable_is_structural() {
     let f = Unforgeable::new().unwrap();