Document that hvPlot works with `quarto preview` if you add `hvplot.extension()`

If you are using hvPlot with Quarto the plots are not shown when `quarto preview` rerenders. See https://github.com/quarto-dev/quarto-cli/issues/8030.

The solution is to add the line `hvplot.extension()`.

I think that this workaround should be applied automatically behind the scenes if it can or documented somewhere.

## This works

https://github.com/holoviz/hvplot/assets/42288570/bd75e925-6cbd-4058-b1df-8695ad46a2b7