Previously, running chkip without any arguments attempted to resolve None
as a domain, resulting in misleading output like "No A record".
This commit adds a check to print the usage line if neither a domain nor
the --me flag is specified. This improves usability and makes the tool behave
more predictably when called without arguments.
The --me flag now respects the --json option. When used together,
chkip will return local and public IP addresses as structured JSON.
This allows easier integration into scripts or tools that consume JSON,
while maintaining human-readable output as the default.
Additionally, CGNAT detection is included in the JSON object as a boolean flag.
This commit introduces the --me flag, which allows users to quickly display
their current local IPv4 and public IPv4/IPv6 addresses.
The public IPs are retrieved using ifconfig.me via curl, ensuring accurate
detection even in CGNAT or split-DNS scenarios. Local IPv4 is determined
via the system's active route through the configured resolver.
The output also includes a CGNAT detection based on private IP ranges and
the reserved 100.64.0.0/10 block, providing a helpful warning if detected.
IPv6 privacy extensions are common, so local IPv6 detection has been removed
to avoid redundant or unstable information.
