feat(plugin-webview): support domStorageAccess for ArkWeb DOM storage

[Islatri]

Linked Issues

Closes #76

Summary

Add a dom_storage_access option to WebviewCreateRequest, threaded through the
named N-API ohos.webview.CreateRequest into the ArkTS WebviewPlugin, so
callers can control ArkWeb's DOM storage (localStorage/sessionStorage).

Motivation

ArkWeb disables DOM storage by default unless .domStorageAccess(true) is
explicitly set on the Web() component. The plugin never sets it, so:

• window.localStorage is null
• frontends throw Cannot read properties of null (white screen)
• token / settings / history cannot be persisted

Android and iOS WebViews enable DOM storage by default, so this is a platform
gap every webview consumer hits on OpenHarmony.

Changes

• crates/plugin-webview/src/lib.rs: add dom_storage_access: Option<bool> field
  • dom_storage_access(bool) builder method to WebviewCreateRequest; extend the
    create_request_retains_optional_value_semantics test.
• plugins/webview/src/main/ets/WebviewPlugin.ets: add domStorageAccess? to
  WebviewCreatePayload, pass it through WebviewSurface.create, and call
  .domStorageAccess(data.domStorageAccess ?? false) in BuildWebview.
• demo/.../types/*/Index.d.ts: regenerate the WebviewCreateRequest declaration
  with the new field.

Default behavior

Defaults to disabled (?? false), matching ArkWeb's official documented
behavior that DOM storage is off unless explicitly enabled. This is a breaking
change in behavior from the previous commit (which defaulted to true), but
aligns with the platform's native default and the official ArkWeb API
specification.

Per ArkWeb documentation:

When domStorageAccess is not explicitly called, DOM Storage API is disabled by default.
Passing undefined or null results in false.

Callers that need DOM storage must explicitly opt in with
.dom_storage_access(true).

Breaking Change Note

This is a behavioral breaking change for existing consumers that rely on the
previous commit's default-enabled behavior. If you are upgrading from the
intermediate commit where default was true, please explicitly set
.dom_storage_access(true) in your WebviewCreateRequest to preserve
functionality.

If this breaking change is unacceptable, the default can be flipped back to
true in WebviewPlugin.ets.

Verification

• cargo check -p openharmony-ability-plugin-webview passes.
• cargo test -p openharmony-ability-plugin-webview --lib (runs in CI with the
  OHOS toolchain; the host cannot link the OHOS .lib sys crates).

[Islatri]

哦其实我更倾向于和ArkWeb的行为保持一致，默认关闭，但提供一个接口可以开启的话就行，但是早上时间仓促AI默认给他开了，这个得晚上下班之后回来再调了

[Islatri]

嗯很好，现在和文档里面描述的一样，是默认关闭了