As a data manager, in the UI I would like to see the names of all the columns when previewing a file

[timcadman]

Is your feature request related to a problem? Please describe.
Currently when you preview a file, if the dataset contains more columns than will display on the page this is indicated with '+ xx more'

Describe the solution you'd like
It would also be useful to see the names of the columns which exist but are not displayed. Attached is a screenshot of how this is managed with the tibble package, which I think is quite neat.

Additional context