Enable copying files from tmate session via scp

[franpog859]

As a developer, I want to be able to easily download files from the tmate session. When debugging, I want to gather logs, connection dumps, and other data that could not be easily copied via ctrl+c or analyzed in the session. It'd be great to do it via scp, like scp 123qwe@lon1.tmate.io:/test.pcapng ./test.pcapng. Currently, it's not implemented and it fails with:

scp 123qwe@lon1.tmate.io:/test.pcapng ./test.pcapng`
Connection to lon1.tmate.io closed by remote host.
scp: Connection closed

There was an issue pointing out that it doesn't work. I want this one to be a suggestion for implementing such a feature