Add .show method on HoloViews elements

[ahuang11]

Since Panel is already a dependency, I think it's just wrapping the element in pn.panel(el).show()

[hoxbro]

No problem with adding this. I have been thinking about doing something similar for .servable.

One of the problems with .servable for me was what to return when calling the method if the returned object should be a panel object or holoviews by doing the same wrapping as you suggest.

I don't think will be a problem for .show.

[philippjfr]

Note that while I have no strong opinions about this and have I think proposed this in the past. This does go against the core design principle of HoloViews which is that elements are declarative containers and have next to no "rendering" related methods or state.