Update performance tests

[h5rdly]

Hi,

First of all, cudos for this sweet library!

The Readme links to a performance test -
https://parallel-ssh.org/post/parallel-ssh-libssh2/

However, this test is from 2017.

Would it be possible to update the tests (perhaps here on github), and add newer libraries like asyncssh to the comparison?

Thanks,
Eli