Publishing the copyrights and licenses of the third party libraries

Some of the third party libraries that Envoy uses have license terms that demand that the copyright or the license itself is included in the software and/or documentation.

For example, [the nghttp2 library uses the MIT license](https://github.com/nghttp2/nghttp2/blob/master/COPYING). It contains this sentence: "Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to [...], subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software."

How does Envoy comply with this legal requirement?

I think the copyright notice and the license of nghttp2 (and other third-party libraries) should appear somewhere in Envoy's documentation. There is already a [table that lists all third-party libraries](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/security/external_deps). A similar table that contains a list of the external dependencies, their licenses and (if necessary) also the complete license texts would solve this problem.