Improve the experience of users coming from Pandas

[maximlt]

Pandas users are likely to be an important fraction of hvPlot users and are probably already used to the Pandas .plot API, having built some expectations on how it is supposed to work. I suggest we try to better document how these users can migrate to hvPlot's API.

Here are some of the key bits I wish were documented explicitly:

• Getting started/entry point for Pandas users specifically
• Enabling hvPlot via setting the Pandas plotting backend or hvplot.pandas import with pros and cons (see Orient Pandas users more towards .plot or .hvplot? #1485 for a more extended discussion)
• Supported plot methods (e.g. pie not available in hvPlot)
• Important API differences. For example, hvPlot has no figsize but width/height, no ax but +/* for composability (see

  hvplot/hvplot/converter.py

  Lines 1550 to 1566 in d2bce93

  	if 'ax' in mismatches:
  	mismatches.pop(mismatches.index('ax'))
  	param.main.param.warning(
  	'hvPlot does not have the concept of axes, '
  	'and the ax keyword will be ignored. Compose '
  	'plots with the * operator to overlay plots or the '
  	'+ operator to lay out plots beside each other '
  	'instead.'
  	)
  	if 'figsize' in mismatches:
  	mismatches.pop(mismatches.index('figsize'))
  	param.main.param.warning(
  	'hvPlot does not have the concept of a figure, '
  	'and the figsize keyword will be ignored. The '
  	'size of each subplot in a layout is set '
  	'individually using the width and height options.'
  	)

  ). There are for sure more important differences to document.
• Important Pandas features not yet available in hvPlot's API but via HoloViews directly (e.g. dual axis)
• Saving a plot

The website currently has the Pandas API guide that is a slightly modified and extended version of the Pandas Visualization Guide. I quite like the concept of this page, trying to replicate Pandas' docs using hvPlot directly (serving both as a test for us and as "migration/compatibility" guide for users. @Azaya89 has opened #1482 to update it based on the latest changes in Pandas docs.

@Azaya89, based on my suggestions above, can you brainstorm and suggest how this content should be organized based on the Diataxis framework (tutorial/how-to/reference/explanation)?

[maximlt]

A small thing; Pandas' users calling .plot in a Jupyter notebook got used to add ; to their call to hide the not-very-useful Matplotlib repr:

When migrating to hvPlot, users should remove ending ; as that would completely hide the hvplot output.