Include the missing license files for upstream OpenWrt packages

[GeorgeSapkin]

This repo includes sources lifted directly from the upstream OpenWrt packages repo. The upstream repo is distributed under the GNU General Public License v2.0:

https://github.com/openwrt/packages/blob/master/LICENSE

When distributing derived works, the source code of the work must be made available under the same license.

Example: https://github.com/gl-inet/gl-feeds/blob/v4.7/golang/golang/Makefile
Upstream: https://github.com/openwrt/packages/blob/master/lang/golang/golang/Makefile