JavaScript externs model StorageEvent() with no type argument

從 javascript/externs/web/webstorage.js 開始，將 StorageEvent 建構函式和 initStorageEvent 的宣告與 issue 中描述的目前 Web IDL 進行比較。更新 extern 簽章，使文件中說明的型別和選用引數得到表示，然後驗證所示的有效建構函式用法不再被建模為零引數。

Description

javascript/externs/web/webstorage.js still models StorageEvent as a zero-argument constructor:

/**
 * @see http://www.w3.org/TR/2011/CR-webstorage-20111208/#the-storage-event
 * @extends {Event}
 * @constructor
 */
function StorageEvent() {}

Current HTML (the-storageevent-interface) defines:

constructor(DOMString type, optional StorageEventInit eventInitDict = {});

new StorageEvent('storage', { key, newValue, ... }) is valid in browsers (constructor available since 2018). CodeQL 2.27.0 reported a false positive on a standards-conforming new StorageEvent('storage', { ... }) call used in a synthetic StorageEvent test.

initStorageEvent in the same file also follows the old required-argument list; the spec method has optional arguments after type.

I searched this tracker for StorageEvent / StorageEventInit / webstorage externs and did not find an existing issue.

Reproduction

1. Analyze JavaScript that constructs new StorageEvent('storage', { key: 'k', newValue: 'v' }).
2. Observe a CodeQL alert that treats the constructor as taking no parameters.

Expected

Externs should match the current constructor (type plus optional StorageEventInit) so valid Web IDL usage is not flagged.

This is a modeling/false-positive report only. No exploit is claimed.