Copyright for rust-gl-generator source package in Mantic

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: gl_generator
Upstream-Contact:
 Brendan Zabarauskas 
 Corey Richardson
 Arseny Kapoulkine
Source: https://github.com/brendanzab/gl-rs/

Files: *
Copyright: 2015-2016 Brendan Zabarauskas and the gl-rs developers
License: Apache-2.0

Files: debian/*
Copyright:
 2021-2022 Debian Rust Maintainers 
 2021-2022 James McCoy 
License: Apache-2.0

License: Apache-2.0
 Debian systems provide the Apache 2.0 license in
 /usr/share/common-licenses/Apache-2.0