Feature Request: Add navigation state APIs

[tuyangJs]

Summary

wry provides basic navigation functions like reload() and navigate(), but lacks a consistent cross-platform API for navigation control and state querying.

For building browser-like applications, Electron-style navigation APIs are expected but currently incomplete in wry.

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Missing APIs

Please consider exposing basic navigation control APIs:

webview.go_back();
webview.go_forward();

webview.can_go_back() -> bool;
webview.can_go_forward() -> bool;