v2.8.8 Move back/forth between subtitles, subtitle format, brightness controls

Synched with https://github.com/lrorpilla/jidoujisho v2.8.8

Additionally:

• Move back and forth between subtitles while playing video.
• Select subtitle font, color, select outline color.
• Hardware keys playback control - b p f - back, play/pause, forward.
• Brightness volume control.
• Bottom bar toggleable always on/off.
• Some other settings.