Pop a tiny spinner next to the cluster selection module while computing clusters with Introduction Weight Heuristic

[sidneymbell]

Relevant reducers: "clustering method selected" and "clustering results updated"

E.g., next to "Introduction Weight Heuristic" title? cc @Janeece

[Janeece]

You could definitely put it next to selection title, I think it would effectively communicate.

You could also consider putting it at a more universal space, like inline with the "Select Clustering algorithm" or at the bottom of the section (which would give you room to add a loading message, if that's needed).