app,internal/window: extract native window code to separate package

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

app/internal/window/runmain_ios.go

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// +build darwin,ios
+
+package window
+
+import "C"
+
+//export gio_runMain
+func gio_runMain() {
+	runMain()
+}