IPv6 isMulticast method is not complete

[CapnCrunchsna]

The IPv6 isMulticast() is only checking that the IP's type is 'Multicast' (see here). The available types include numerous other multicast types with descriptions that look to be straight from the spec.

The isMulticast() method should include checks for all of the multicast types, or do a .includes(...) check instead of === for the 'Multicast' string.