Add plot_ts

[aloctavodia]

Conditional on what happens with #317

[rohanbabbar04]

Is this issue still open?

[aloctavodia]

Yeah, we have plot_lm but not plot_ts. Not sure if we also want it, or we need to extend plot_lm. I think is ok to have it, even if similar.

[rohanbabbar04]

Great, I will work on this then.

[jinukuntlaakhilakumargoud-web]

Hi! I'm interested in working on this issue. I've looked at plot_lm and the legacy arviz.plot_ts. Should I implement plot_ts as a standalone new function or extend plot_lm? Looking forward to your guidance!