Integrate Codspeed to track benchmarks

[webknjaz]

https://codspeed.io

[webknjaz]

Somebody has to approve the https://github.com/apps/codspeed-hq app install into the org.

[webknjaz]

Alright, gundalow approved it. So we'll be able to make use of it now. I've provisioned a secret into the repo. The next step would be to write some benchmarks with pytest-codspeed via https://codspeed.io/docs/benchmarks/python and integrate GHA: https://codspeed.io/docs/integrations/ci/github-actions.