chore: move windows extras to standalone cli_windows example

examples/dart/cli_windows/native/thermion_window.h

@@ -0,0 +1,64 @@
+#pragma once
+
+#pragma comment(lib, "Shlwapi.lib")
+#pragma comment(lib, "opengl32.lib")
+#pragma comment(lib, "dwmapi.lib")
+#pragma comment(lib, "comctl32.lib")
+#pragma comment(lib, "Gdi32.lib")
+#pragma comment(lib, "User32.lib")
+
+#ifdef _WIN32
+#ifdef IS_DLL
+#define EMSCRIPTEN_KEEPALIVE __declspec(dllimport)
+#else
+#define EMSCRIPTEN_KEEPALIVE __declspec(dllexport)
+#endif
+
+#include <cstdint>
+#include <iostream>
+#include <Windows.h>
+
+namespace thermion {
+
+///
+/// Instantiating a ThermionWindow creates a HWND that can be passed 
+/// to Filament to create a swapchain.
+///
+///
+class ThermionWindow {
+    public:
+    ThermionWindow(
+        int width, 
+        int height, 
+        int left,
+        int top);
+    HWND GetHandle();
+    void Resize(int width, int height, int left, int top);
+    private:
+        HWND _windowHandle;
+        uint32_t _width = 0;
+        uint32_t _height = 0;
+        uint32_t _left = 0;
+        uint32_t _top = 0;
+};
+
+static ThermionWindow* _window;
+
+extern "C" { 
+    EMSCRIPTEN_KEEPALIVE intptr_t create_thermion_window(int width, int height, int left, int top) { 
+        _window = new ThermionWindow(width, height, left, top);
+        return (intptr_t)_window->GetHandle();
+    }
+
+    EMSCRIPTEN_KEEPALIVE void update() {     
+        MSG msg;
+        if(GetMessage(&msg, NULL, 0, 0))
+        {
+            TranslateMessage(&msg);
+            DispatchMessage(&msg);
+        } 
+    }
+}   
+
+}
+#endif