[scikit-image] Comparison of watershed implementations

I wish the authors also compared accuracy, but here are their performance benchmarks. No surprises :) https://www.mdpi.com/2313-433X/4/10/123/pdf "An Overview of Watershed Algorithm Implementations in Open Source Libraries", J. Imaging 2018, 4(10), 123; https://doi.org/10.3390/jimaging4100123, Anton S. Kornilov and Ilia V. Safonov. Best regards, Stéfan