This function lets the user download a file from Dropbox, specifying its name and using a previously created token.
db_download(filename, xlsx = TRUE, token_dir = NA,
token_name = "token_pers.rds")
String. File's name
Boolean. Is it an Excel file? Can be returned as a list for each tab and not as a file if needed
Character. RDS with token local directory
Character. RDS file name with your token's data