PixelPaint: Close New Image dialog after pressing return key

13e526de43847ac86d74e3cb0be2d6b930f1d46f added the feature to new Layer
dialog. This patch adds it to Image dialog to stay consistent across
the app. :^)

Userland/Applications/PixelPaint/CreateNewImageDialog.cpp

@@ -65,6 +65,10 @@ CreateNewImageDialog::CreateNewImageDialog(GUI::Window* parent_window)
         m_image_size.set_height(value);
     };
 
+    m_name_textbox->on_return_pressed = [this] {
+        done(ExecOK);
+    };
+
     width_spinbox.set_range(1, 16384);
     height_spinbox.set_range(1, 16384);