[Feature] Count album_track_num up across multiple volumes

[wataa47]

Current Situation

Currently when an album has multiple volumes the track counter is reset for every volume

Suggestion / Feature Request

The track counter should increase across volumes.
For example if volume 1 has 15 tracks the first track of volume 2 should have number 16.

[exislow]

You can use {track_volume_num} for volume numbering. It doesn't count up as you suggest but it can prefix the volumes like:

101, 102, 104, ..., 201, 202, 203, ...

But feel free to get me a PR for this.