Method for captioning plots `df.hvplot.caption()` or `hvplot.caption()`

I'm creating a explanatory visualization and it'd be awesome if hvplot had a caption method so you can do something like

`df.hvplot.bar("date", "arr") * df_sum.hvplot.caption("Total ARR {arr} from {ini_date} to {end_date}")`

Or even `df.hvplot.bar("date", "arr", caption=f"Total ARR {arr} from {ini_date} to {end_date}", caption_loc="bottom_left")`