Good First Issues in Haxe

As more and more low-level changes get implemented into the HScriptedClass implementation, we should definitely create a test suite to include a set of scripts aimed at ensuring functioning language features and preventing regressions. Hooking that up to Github Actions (the public runner should be sufficient for this since Polymod is way smaller than a full game) would allow quickly evaluating if something got broken by a commit before deployment. So far, the main obstacle is the fact I haven't found a testing library that behaves politely with Lime, so that might even necessitate creating a custom one. Flixel uses munit but I found that to be a pain in the ass when working with Funkin' so we'll have to see.