feat: resolves #57 : add support for "arrangement" option in plot_annotation method

[janaab11]

def plot_annotation(..., arrangement="pack"):
    ...

When arrangement is:

• pack: follows default grouping, by timestamps only
• stack: groups segments by their label. Each label gets a distinct line

[hbredin]

Thanks! Will definitely have a look at this PR but with summer vacations coming up, I cannot promise any ETA...

[hbredin]

It took a long time but I finally managed to have a closer look at the code.

I think I'd prefer the API to look like this:

from pyannote.core import notebook
notebook.set_arrangement("stack")  # defaults to "pack"

This way, it can also be used directly by Jupyter Notebook cells returning Annotation instances, without having to call plot_annotation manually.

See Segment.set_precision for ideas on how to implement this API