add function description to read_datmonth() and rbind_files_addname()
These functions need a few words description, parameters in and out here: https://git.noc.ac.uk/brecinosrivas/icoads.utils/-/blob/master/R/read_rdsfiles.R#L88-94
https://git.noc.ac.uk/brecinosrivas/icoads.utils/-/blob/master/R/read_rdsfiles.R#L179-185
Needs documented also in the Wiki.
Is best if @eck can comment below and I will add it.