app: add code for macOS and Windows apps under 'app' (#12933)

* app: add code for macOS and Windows apps under 'app'

* app: add readme

* app: windows and linux only for now

* ci: fix ui CI validation

---------

Co-authored-by: jmorganca <jmorganca@gmail.com>

app/webview/glue.c

@@ -0,0 +1,36 @@
+#include "webview.h"
+
+#include <stdlib.h>
+#include <stdint.h>
+
+struct binding_context {
+    webview_t w;
+    uintptr_t index;
+};
+
+void _webviewDispatchGoCallback(void *);
+void _webviewBindingGoCallback(webview_t, char *, char *, uintptr_t);
+
+static void _webview_dispatch_cb(webview_t w, void *arg) {
+    _webviewDispatchGoCallback(arg);
+}
+
+static void _webview_binding_cb(const char *id, const char *req, void *arg) {
+    struct binding_context *ctx = (struct binding_context *) arg;
+    _webviewBindingGoCallback(ctx->w, (char *)id, (char *)req, ctx->index);
+}
+
+void CgoWebViewDispatch(webview_t w, uintptr_t arg) {
+    webview_dispatch(w, _webview_dispatch_cb, (void *)arg);
+}
+
+void CgoWebViewBind(webview_t w, const char *name, uintptr_t index) {
+    struct binding_context *ctx = calloc(1, sizeof(struct binding_context));
+    ctx->w = w;
+    ctx->index = index;
+    webview_bind(w, name, _webview_binding_cb, (void *)ctx);
+}
+
+void CgoWebViewUnbind(webview_t w, const char *name) {
+    webview_unbind(w, name);
+}