Enable DNS Resolution

[hanno2003]

This pull request enhances the initIPBlocks function in plugin.go to support both CIDR block parsing and DNS resolution for input strings. This change increases the flexibility of the function by allowing it to handle domain names in addition to CIDR blocks.

Enhancements to initIPBlocks function:

• The function now attempts to parse each input string as a CIDR block first. If parsing fails, it falls back to resolving the string as a domain name via DNS.
• For resolved domain names, the function converts the resulting IP addresses into /32 (for IPv4) or /128 (for IPv6) CIDR networks before adding them to the list of IP networks.
• Improved error handling ensures that meaningful error messages are returned when neither CIDR parsing nor DNS resolution succeeds.