Include Debian copyright file.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>

debian/copyright

@@ -0,0 +1,23 @@
+Format: http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Name: qtmips
+Source: https://github.com/cvut/QtMips/
+
+Files: *
+Copyright: 2017-2019 Karel Koci<cynerd@email.cz>
+           2019      Pavel Pisa <pisa@cmp.felk.cvut.cz>
+License: GPL-2.0+
+ 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 2 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 <http://www.gnu.org/licenses/>.
+ .
+ On Debian systems, the complete text of the GNU General Public License
+ Version 2 can be found in `/usr/share/common-licenses/GPL-2'.