Show number of columns in the summary row

[RandomFractals]

Latest version of this data grid displays the number of data rows in a grid footer.

I think it would be valuable to see the number of columns there too, similar to how most data frame libraries display them now.

Example of df.head table display:

Also, I was able to integrate it into VSCode Data Table renders extension and plan to ship that update soon.

I hope this addition will improve datasets preview in VSCode Jupyter notebooks. Example:

Extension: https://marketplace.visualstudio.com/items?itemName=RandomFractalsInc.vscode-data-table

[Wattenberger]

makes sense! and looks great in the vscode ui!