Reorder elements in player

[fe51]

Ciao,

@MateoLostanlen thanks for the quick UI fix in #254 !

To have a better render, I suggest the following modifications :

• Move the slide at the right of play/pause button (hence move the "display: 10 and toggle button" to the right
• Center vertically toggle button and the related text
• Center vertically the slider

You can see the suggestion in the screenshot below

Thanks a lot for your help !