Allow setting xaxis/yaxis as string

[ahuang11]

Like xaxis="top" "bottom" etc
https://holoviews.org/user_guide/Customizing_Plots.html#axis-positions

[maximlt]

Would it also be OK for you to use an enum like hvplot.AXIS_LOC.Top (naming can be improved)?

[ahuang11]

Yeah I'm fine with that, as long it supports both (i.e. "top" and hvplot.AXIS_LOC.Top)--the enum will simply check if the string is valid and cast as necessary.

If enums are a thing, I think they should be implemented in HoloViews, and hvPlot imports it.