write base64 result to file

This is a helper function to write some resulting data from chrome to file. It will:

• decode the base64 encoded raw data

• write to file using base::writeBin() It will be useful for function like Page$printToPDF()

write_base64(res, con)

Arguments

res	A resulting list object with some data field containing base64 encoded data. (like Page$printToPDF())
con	A connection object. See base::writeBin().