Initiate hello-clusters

[sjspielman]

Closes #793

This PR establishes the hello-clusters module:

• I didn't include the analysis template directories (plots, scratch, & results) since I don't think they are necessary for this module, which I anticipate will just have some example notebooks at the top level. Do you foresee something I don't?
• I added an initial description to the README, including a brief overview of the functions this module will present and how to install rOpenScPCA. As notebooks get added, the README will be expanded accordingly.
  • I put in an instruction for force=TRUE, but I don't think I like that I did that? I imagine when there are relevant-enough changes we'll bump the package version itself and renv::update() maybe should be used instead?
• I added an initial (mostly empty) notebook which will get filled in as part of Add notebook to demonstrate clustering with rOpenScPCA #796. I added this to be able to load libraries that allowed me to build up the renv.lock file. I also added an, essentially empty for now, script to run the module which will likely just be used for testing
• The Dockerfile is ready to go as well, but I didn't activate the build docker workflow yet. But, if we want to actually just get the run module workflow up and running with a Docker environment from the get-go, maybe now is actually the time so the next PRs can use it!

[jashapiro]

This looks good for the start of the repo. One typo fix I saw, and the comments below (tl;dr: do add back the standard directories).

I had some interesting trouble installing at first with your directions and a slightly nonstandard renv setup, but I think the fix for that can go elsewhere.

• I didn't include the analysis template directories (plots, scratch, & results) since I don't think they are necessary for this module, which I anticipate will just have some example notebooks at the top level. Do you foresee something I don't?

I would include these, as they don't hurt at all. You can also have the notebooks save some results (multiple clustering results as a table) and plots. I think it is good to demonstrate this even in a simple module like this.

[jashapiro]

I don't think there is any reason not to activate this if it is ready to go.