[Net\mail] raise error, if there is no configuration provided whatsoever

[github-actions[bot]]

[Net\mail] raise error, if there is no configuration provided whatsoever perhaps, this could be also done in a more "templated" way; at least, for Config values

https://github.com/arturo-lang/arturo/blob/411617a1906063cf0adfd3ac06804dc4b29403a0/src/library/Net.nim#L155

                    retrieveConfig("mail", "using")

                    # TODO(Net\mail) raise error, if there is no configuration provided whatsoever
                    #  perhaps, this could be also done in a more "templated" way; at least, for Config values
                    #  labels: library, bug

319821564afd410c403137f53d1417b9d3436a49