Add unit test workflow

[Ark2000]

By utilizing this great project: https://github.com/bitwes/Gut

A good reference: https://github.com/bitbrain/beehave/blob/godot-4.x/.github/workflows/unit-tests.yml

[Eggbertx]

I got GUT working and created a simple input test, but Godot isn't playing nicely with the GitHub workflow VM. https://github.com/Eggbertx/PankuConsole/actions/runs/6839651321/job/18598061573#step:4:19 The command works fine and has a 0 exit code when I run it on my own computer, but it's crashing when run in the workflow. I've tried with xvfb-run (a virtual framebuffer X server) and without it, using Godot's --headless command line argument. Both result in it crashing with "Debugger Break, Reason: 'Parser Error: Could not find type "PankuLynxWindowsManager" in the current scope.'"

[Ark2000]

I got GUT working and created a simple input test, but Godot isn't playing nicely with the GitHub workflow VM. https://github.com/Eggbertx/PankuConsole/actions/runs/6839651321/job/18598061573#step:4:19 The command works fine and has a 0 exit code when I run it on my own computer, but it's crashing when run in the workflow. I've tried with xvfb-run (a virtual framebuffer X server) and without it, using Godot's --headless command line argument. Both result in it crashing with "Debugger Break, Reason: 'Parser Error: Could not find type "PankuLynxWindowsManager" in the current scope.'"

bitbrain is using gdUnit4 as beehave's test tool, maybe gdUnit4 is a better option other than GUT

[Eggbertx]

Alright, it works with gdUnit4. Though at the moment the only thing that's being tested is that the module manager is initialized and working correctly, and that the shell opens when the ~ key is "pressed" and closes when it's "pressed" again.