use codspeed to benchmark performance and look for regressions

[beckermr]

We can use this free service to write benchmark tests for CPUs: https://docs.codspeed.io/benchmarks/python

We won't be able to test on GPUs, but it will be a good start.

[ismael-mendoza]

I think you implemented this already in #100 so we can close this issue?

[beckermr]

I'd like to implement other bits of the code.