app/internal/app: introduce runOnMain for main thread callbacks

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/window/os_darwin.m

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+@import Dispatch;
+
+#include "os_darwin.h"
+#include "_cgo_export.h"
+
+void gio_wakeupMainThread(void) {
+	dispatch_async(dispatch_get_main_queue(), ^{
+		gio_dispatchMainFuncs();
+	});
+}