Familiarization with diffimTests repository

The Git repository at https://github.com/lsst-dm/diffimTests contains a bunch of scripts, notebooks and other artefacts relating to tests carried out on image differencing in the LSST context. Take an inventory of this repository, experiment with the contents, and find out if there is material there that we can learn from in the short term and/or should preserve for posterity as important results.

When both this ticket and DM-16409 are complete, you should be able to give us a concise overview of what image differencing functionality is available within the LSST codebase and what tests have been performed on it, together with a summary of any key results.