Wrap docstrings earlier to avoid lines spilling over in the JupyerLab help pop up

[joelostblom]

I suggest shortening the lines of the docstrings so that they wrap nicely in the JupyterLab help popup (Shift + Tab). Here is an example of what I mean (the docstring in the images is not from altair but the behavior is the same as in e.g. the "Attributes" section of alt.Chart).

Current:

Suggested:

I did this previously for plotly and I believe the exact line width that jupyterlab breaks at is 76, so I can reformat the docstrings to break at 75 to maximize space or 72 if you prefer to follow the pep8 suggestion (I am fine with either, I just don't want the lines to spill over since I think they are hard to read then).

I don't know if this can be automated somehow with black, but if not I can change them all manually if you think this would be a useful change. Are they all in vegalite/v4/api.py?

[joelostblom]

I also suggested JupyterLab to change the width of the help pop-up since that would be the more general solution. (and I remembered part of altair is programmatically generated from vegalite so manual modification might not be the way to go here)

[joelostblom]

This was just merged in JL master and will be in 3.0 jupyterlab/jupyterlab#9134

So instead of the current popup that looks like this for many altair functions:

You will be able to see more of the documentation in both directions: