Add option to keep player visible during slideshow

[Domovoy424]

Steps to reproduce the behavior: 1.Run Nomacs 2.Go to «Панели» 3.Check the box on «Проигрыватель» 4.Click on «Воспроизвести /остановить» in the panel «Проигрыватель» 5. Go to «Панели» 3.See error. The box is not checked, panel is not displayed

Expected behavior The panel is displayed

• OS: Windows 10 pro X64
• Version Nomacs 3.16.1709 [x64]

[scrubbbbs]

Translation:

Steps to reproduce the behavior:
Run Nomacs
Go to Panels
Check the box for Player
In the Player panel, click Play / Stop
Go back to Panels
See error: the box is not checked, and the panel is not displayed

Expected behavior
The panel should be displayed

The player is auto-hidden during the slideshow, and so the panels checkbox is behaving correctly. But we do not have an option to keep the player visible during the slideshow.