Add -c flag to select command

[JoshCheek]

See cc3653c for more on the -c flag.

Example of why this is useful:

fetch https://raw.githubusercontent.com/andrab/ecuacovid/master/datos_crudos/ecuacovid-vacunas.csv | save ecuacovid-vacunas.csv
let names = (open ./ecuacovid-vacunas.csv | get | last 2);
open ./ecuacovid-vacunas.csv | select informacion -c $names

Co-authored-by: Andrés N. Robalino andres@androbtech.com

[sophiajt]

Thanks!