add support for Apple Pencil and build for iOS

engine/app_events.cpp

@@ -11,6 +11,20 @@ void App::resize(float w, float h)
         main->update(w , h, zoom);
 }
 
+void App::showKeyboard()
+{
+#ifdef __IOS__
+    [ios_view becomeFirstResponder];
+#endif
+}
+
+void App::hideKeyboard()
+{
+#ifdef __IOS__
+    [ios_view resignFirstResponder];
+#endif
+}
+
 bool App::mouse_down(int button, float x, float y, float pressure)
 {
     MouseEvent e;