Add bluster functions to cheatsheet

[sjspielman]

Closes #813

This PR adds bluster functions used in the (forthcoming) exercise notebook to the scRNA-seq-advanced.

A couple additional questions:

• I also realized we don't have bluster in the scRNA-seq cheatsheet. Should I go ahead and add clusterRows() there too?
• I haven't done ☝️ (yet) in case we think I should also add NNGraphParam() (and/or KGraphParam() KMeansParam() which is also used in the scRNA-seq module), so I'll do this all in one go if we want to add more!

[sjspielman]

Given https://github.com/AlexsLemonade/exercise-notebook-answers/pull/228/files#r1861067009, I'm thinking I should go ahead and add NNGraphParam() and KGraphParam().

[jashapiro]

Given https://github.com/AlexsLemonade/exercise-notebook-answers/pull/228/files#r1861067009, I'm thinking I should go ahead and add NNGraphParam() and KGraphParam() KMeansParam()*.

I was just about to say this. And you may as well add it to the scRNA-seq cheatsheet while you are doing this.

[sjspielman]

@jashapiro done!

[jashapiro]

I did a bit of rewording, and fixed a function name. See what you think of the rewords.

[jashapiro]

LGTM (Though I am baffled by the size changes for the PDFs)

[sjspielman]

Though I am baffled by the size changes for the PDFs

Wow that is baffling...