Add European Union Public Licence templates
The EUPL-1.2 is as a licence written to be compatible with recent versions of the GPL among other licences but written in such a way that it is better adapted to the copyright law of European Union member states. There are two previous versions, 1.1 and 1.0, but I am not sure whether there is any particular value in including those given that they are older versions and I am not sure whether they have any reasons to be preferred.
Additionally, according to SPDX, there is no standard licence header for the EPL-1.21. As such, I wrote one based on the MPL-2.0 licence header already used in Builder.