Add add_copyright.py.
Add add_copyright.py.

fuchsia-mirror/third_party-shaderc,dneto0/shaderc,Samana/shaderc,drewet/shaderc,Qining/shaderc,Qining/shaderc,davidlee80/shaderc,antiagainst/shaderc,antiagainst/shaderc,dneto0/shaderc,AWoloszyn/shaderc,fuchsia-mirror/third_party-shaderc,antiagainst/shaderc,Samana/shaderc,Qining/shaderc,Samana/shaderc,AWoloszyn/shaderc,fuchsia-mirror/third_party-shaderc,dneto0/shaderc,antiagainst/shaderc,davidlee80/shaderc,davidlee80/shaderc,AWoloszyn/shaderc,dneto0/shaderc,drewet/shaderc,drewet/shaderc