Add a function to compute sibling networks

[rye]

Inspired by https://github.com/dspinhirne/netaddr-rb/blob/38a4a64300a2a9d228bcaf436bea8f368bc20fc5/lib/ipv4net.rb#L97-L104, write a method that allows for the computation of sibling networks. For example, the next sibling of 127.0.0.0/24 is 127.0.1.0/24?

• Verify what the netaddr gem does.
• Decide on a better path here, if one exists.