Copyright for xe source package in Bionic

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: xe
Source: https://github.com/chneukirchen/xe

Files: *
Copyright: Copyright (c) 2015-2017 Leah Neukirchen 
License: CC0-1.0

Files: debian/*
Copyright: Copyright (c) 2017 Nicolas Braud-Santoni 
License: CC0-1.0

License: CC0-1.0
 To the extent possible under law, the author(s) have dedicated all copyright
 and related and neighboring rights to this software to the public domain
 worldwide. This software is distributed without any warranty.
 .
 The full text of the CC0 1.0 Universal license is available on Debian systems
 in /usr/share/common-licenses/CC0-1.0