Suggestion: improved doc for running tests / testing on MacOS 13

Thank you for linux-timemachine. Exactly what I was looking for. I like the focus on testing.

I want to use timemachine on MacOS13 and want to run all tests before really using it. I cannot find info on how to do this (I have written a runall.sh, but it fails with a docker error message - Unable to find image 'cytopia/ssh-server:latest' locally on test 10 Remote (absolute path)).

My suggestion: add documentation explaining how to run all tests and if necessary, add a bash file that runs all tests.

If I can figure it out myself, I will generate a pull request.

Note: I have not used github for a long time and am not familiar with how .sh automated tests can be run.