Volume boost/equalizer

[jtechguru1]

Is your feature request related to a problem? Yes. Some Audiobooks are too quiet.

Describe the solution you'd like.

A volume boost built into the application. With pitch and a few equalizer channels.

Describe alternatives you've considered

I installed several different volume boosters that effect all apps. While this works to some degree, this app is literally the only one needing the boost. So when I switch apps, get notifications, or an incoming call the sound is distorted enough that I just revert back and deal without the distorted sound coming from everything else

Additional context

This is a feature many audiobook players have, but those players aren't synced to Audiobookshelf. So my progress wouldn't be tracked across devices.

[advplyr]

Duplicate of #195

[advplyr]

Also #407