wkt2csv: Convert labeled WKT into a CSV

[Notgnoshi]

Convert labeled WKT of the form

label1: POLYGON((...))
label2: POINT(...)

(one WKT geometry per line, prefixed by a label, a common output format if logging from an application)

into CSV file(s) like

$ head polygon.csv
geometry,label
"POLYGON((...))","label1"
$ head point.csv
geometry,label
"POINT(...)","label2"

See: https://github.com/Notgnoshi/dotfiles/blob/master/stowdir/.local/bin/wkt2csv for something similar, but I don't like that it uses the label as prefixes in the CSV file names. I think it should be one file per geometry type, not one file per unique label.