Access Steam features in the Windows WebView2, macOS WKWebView, and Linux CEF exporters. Requires r407.2+ for Windows, r417+ for macOS, and r412+ for Linux.
See the section on the overlay in the documentation. The in-game overlay is not currently supported (Valve need to add support for that), but when the in-game overlay is not supported Steam uses a fallback approach, and that definitely worked for me last I tried.