Make GUI and Widget updatables

engine/src/main/java/com/bartlomiejpluta/base/engine/context/model/DefaultContext.java

@@ -288,6 +288,10 @@ public class DefaultContext implements Context {
          }
       }
 
+      for (var gui : guis) {
+         gui.update(dt);
+      }
+
       for (var iterator = sounds.iterator(); iterator.hasNext(); ) {
          var sound = iterator.next();
          if (sound.isStopped()) {

engine/src/main/java/com/bartlomiejpluta/base/engine/gui/render/NanoVGGUI.java

@@ -56,6 +56,11 @@ public class NanoVGGUI implements GUI {
       screenWidget = new ScreenWidget(screen);
    }
 
+   @Override
+   public void update(float dt) {
+      screenWidget.update(dt);
+   }
+
    @Override
    public void render(Screen screen, Camera camera, ShaderManager shaderManager) {
       if (!visible) {

engine/src/main/java/com/bartlomiejpluta/base/engine/gui/widget/ScreenWidget.java

@@ -237,6 +237,13 @@ public class ScreenWidget implements Widget {
       throw new UnsupportedOperationException();
    }
 
+   @Override
+   public void update(float dt) {
+      if (root != null) {
+         root.update(dt);
+      }
+   }
+
    @Override
    public void draw(Screen screen, GUI gui) {
       if (root != null) {