[FR] Add seek buttons at current song view

[bender21a]

Describe the solution you'd like
Add a forward (e.g. 20sec) and backward (e.g. 10sec) seek button to the playback controls. In addition to the previous and next title buttons.
May it will be possible to set the seek time individually.

• I will follow the issue format and will add [FR] to the start of my issue title, and I acknowledge that if I don't follow the format, my issue might get closed without further explanation.

Great app and battery saver.