Plot waveforms

[liesenf]

Once scikit-talk supplies this functionality, including audio data in the plots becomes within reach:

Description:
the idea is that talkr can utilise the [audio] column in the data frame to print waveforms into the boxes in the plot, similar to how text transcripts are currently rendered.

[bvreede]

This is related to elpaco-escience/scikit-talk#23

[mdingemanse]

Closing as duplicate of #46 but taking note of Barbara's ref to the scikit-talk issue