add river variable list for Med-CORDEX

[sam-somot]

Dear @larsbuntemeyer @jesusff

In Med-CORDEX we have prepared the river variable list already.
Could you please create the csv format ?
You can find it here:
https://docs.google.com/spreadsheets/d/1MKhVceng4_oKnnvBWaDQqz58ywUUajVK/edit?gid=1672965248#gid=1672965248

@erika.coppola is in principle the main contact point but she does not have a github account @graziano_giuliani

[jesusff]

pinging the real @graziano-giuliani

OK, these are very few variables. I can handle them by hand