I added unit testing using the "Unity" framework.
So far, they only test some of the simpler functions in four different files.
The tests are added in a separate directory (/tests) and will not be run unless triggered explicitly with "make tests" in that directory. I have also added this call to the build pipeline.
My plan is to introduce more thorough testing of most of the commands over time.
So far, taking full advantage of github copilot and setting up codeql has let me fix a selection of minor bugs (at least one of which was a crash bug and two potential security problems).
When i introduce more tests, it will become necessary to fix the actual code as well, but I tried to avoid it when adding the test framework, to not get too many unrelated changes.
