This option adds a piece of data, usually a name + value pair, to the
end of the URL query part. The syntax is identical to that used for
--data-urlencode with one extension:
If the argument starts with a '+' (plus), the rest of the string is
provided as-is unencoded.
This allows users to "build" query parts with options and URL encoding
even when not doing GET requests, which the already provided option -G
(--get) is limited to.
This idea was born in a Twitter thread.
Closes#9691
