Copyright for flycheck-package source package in Focal

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

Files: *
Copyright: (C) 2014-2016 Steve Purcell 
               2014-2016 Fanael Linithien 
License: GPL-3+

Files: debian/*
Copyright: (C) 2017-2020 Lev Lamberov 
License: GPL-3+

License: GPL-3+
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 .
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 .
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see .
 .
 On Debian systems, the complete text of the GNU General
 Public License version 3 can be found in `/usr/share/common-licenses/GPL-3'