add support for Apple Pencil and build for iOS

engine/app.h

@@ -15,6 +15,11 @@
 #include "node_panel_stroke.h"
 #include "node_canvas.h"
 
+#ifdef __OBJC__
+#import <Foundation/Foundation.h>
+#import "GameViewController.h"
+#endif
+
 class App
 {
 public:
@@ -51,6 +56,12 @@ public:
 #else
     float zoom = 1.0;
 #endif // __ANDROID__
+    
+#if defined(__IOS__) && defined(__OBJC__)
+    GameViewController* ios_view;
+#endif
+    void showKeyboard();
+    void hideKeyboard();
     void initLog();
     void init();
     void initShaders();