Offer files previews

It would be nice to be able to give a preview of data files declared in Inishell (for example, first 200 lines). This would be useful when declaring something like STATION1 = great_data.csv in order to see the headers and get a quick idea of the file structure, all within Inishell.

This would require an additional (possibly optional) button next to the file selector that would open a new window showing the first n lines of the file (n being hard coded) with line numbering but no additional widgets (no support for file editing or other fancy stuff). Possibly, showing invisible characters would be a great bonus (to see that CR LF are used for end of lines for example).