Mk: add new EUPL license group along with EUPL11 & EUPL12

• see https://interoperable-europe.ec.europa.eu/collection/eupl/eupl-text-eupl-12
• add https://eupl.eu/1.2/en there are now 5 consumers in tree

sysutils/tere
deskutils/ausweisapp2
dns/dog
devel/soapui
net-mgmt/riemann-c-client

PR: 281702
Differential Revision: https://reviews.freebsd.org/D44940
Approved by: mat (portmgr)
Sponsored by: SkunkWerks, GmbH