Show ; attributes... in plot function docstrings

[jariji]

Feature description

We have

help?> scatter

  scatter(positions)
  scatter(x, y)
  scatter(x, y, z)


  Plots a marker for each element in (x, y, z), (x, y), or positions.

  Attributes
  ==========
...

But the signatures don't show that they accept kwargs, so I forget what I'm supposed to do with them. Suggestion: show ; attributes... in the signature.

For plot types, please add an image of how it should look like

  scatter(positions; attributes...)
  scatter(x, y; attributes...)
  scatter(x, y, z; attributes...)


Plots a marker for each element in `(x, y, z)`, `(x, y)`, or `positions`. 
`attributes` can be any of the attributes below.


  Attributes
  ==========