Draft: Resolve "Add flags to enable IPv{4,6} separately"

This update adds new command-line options to allow users to specifically request IPv4 or IPv6 CIDRs from Cloudflare, or both.

The main function and NGINX configuration generation have been modified to respect these new options, only processing and outputting the requested IP versions. This change provides more flexibility in how the script generates NGINX configurations, allowing users to tailor the output to their specific needs.

Closes #2