[Feature Request] Support Constrained K-Means

[hsbadr]

It would be nice to control the minimum cluster size.

[mlampros]

I think the conclust R package offers a constrained k-means algorithm but from what I see the parameter setting of the "ckmeans" function differs compared to the Python implementation which allows to use a "size_min" and "size_max" parameter. This requires to go through papers and it's kind of time consuming. Feel free to make a PR if you intend to create the code base.