Gamification splashscreen issues

• The play button is currently without any function while playing a sound and so is the stop button while there is no sound played.

• The file chooser style is the default browser style and should adapt our corporate design (round borders, 100% width, etc.)

• The title (Voting-Musik) is "denglisch" and should be replaced.

• On mobile devices the button labels are overflowing the button size. The splashscreen gets not centered correctly.

• The volume of the sound is reset when the music file has been changed. The slider remains on the old value.

• When the sound is set to inactive the music preview (clicking on the play button) is not working.