Copyright for yarl source package in Buster

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: yarl
Upstream-Contact: Andrew Svetlov 
Source: https://github.com/aio-libs/yarl/

Files: *
Copyright: Andrew Svetlov 
License: Apache2

Files: debian/*
Copyright: 2016 © Piotr Ożarowski 
License: Apache2

License: Apache2
 See /usr/share/common-licenses/Apache-2.0