- add table rendering for reserved networks
-- note that the IANA doesn't seem to include all? e.g. ff02:: etc.
-- ... that's because it's in a different registry:
	https://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xhtml
	https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml
	see https://www.iana.org/numbers "IP Address Allocations" section

- when checking/rendering reserved networks, currently the footnotes aren't returned.
-- netsplit.IANARegistryFootnote
-- encapsulated in the IANARegistry.Footnotes

- add new interface, Getter? different formatting?
-- (i forget what this was for. carving a smaller subnet out of a subnet?)