[Feature Request] Should have benchmarks

[ralfbiedert]

• What is the feature ?

After working on #56 and #54 I think it would be nice to have some some reference benchmarks to measure if certain changes actually improve or degrade performance, esp. when iterating the CPU-only BitMapBackend.

• Why do you need the feature ?
• What is the use case ?

See above.

[38]

Yes, I saw your benchmark. I believe that is a good start point.

[ralfbiedert]

I just saw you implemented criterion benchmarks. Awesome! This is exactly what I was hoping for, thank you so much!