Spatial clustering example using BayesSpace

[lmweber]

Currently in the clustering chapter, we only have a short example using non-spatial clustering, and then list some alternatives for spatial clustering algorithms. @estellad

We have had good experiences with BayesSpace in our collaborations, and it is available in Bioconductor, so we could include an example using BayesSpace in the clustering chapter.

This would be in addition to using BayesSpace in the new workflow chapters from @estellad.

Here I believe the main constraint may be runtime. For the main examples in the chapters, we want to keep runtime as fast as possible, so that the whole book builds in a reasonable amount of time. Depending on how fast the example is, we could use a sub-region of a full sample or consider subsampling spots if we need to speed up runtime.

Also tagging @stephaniehicks @raphg