Allow downloading data without ssl cert verification

[gromdimon]

Is your feature request related to a problem? Please describe.
Curently s5cmd validates ssl certs when running ./download-data.sh. However, sometimes we do not want to validate them and for that usecase additional flag --no-verify-ssl should be added to s5cmd command.

Describe the solution you'd like
Configure a NO_VERIFY_SSL=${NO_VERIFY_SSL-0} setting and then depending on this add a S5CMD_NO_VERIFY_SSL_ARG command line variable that is empty when ssl veritifcation is wanted and --no-verify-ssl otherwise.

Describe alternatives you've considered
N/A

Additional context
N/A