DOC: plotting backend is not mentioned in the user guide

[jorisvandenbossche]

The new plotting backend option is documented for package authors implementing such a backend: https://dev.pandas.io/docs/development/extending.html#plotting-backends, but we should probably mention this in the user guide (https://dev.pandas.io/docs/user_guide/visualization.html) as well.

[mehersaipreetam]

I would like to work on this please.

[alimcmaster1]

Sure for for it! @mehersaipreetam - write take to assign the issue to yourself :)

[mehersaipreetam]

take

[mehersaipreetam]

Can you please review my pr and see where I'm going wrong?

[alimcmaster1]

Actually it looks like @rushabh-v already has an open PR. (Apologies for my comment above) There are many other good first issues