[ENHANCEMENT/CI] Build Actions for Sample Projects

[NotHyper-474]

Redo of #409, since it apparently got closed because the base branch got deleted. If that was intentional, feel free to reply stating so and close this.

• Implements Add Github Actions to build sample projects on multiple platforms #71

What's left to figure out:

• Maybe find out how to use hmm on Windows with the setup-haxe workflow without having to manually set HAXEPATH. Perhaps Funkin Crew's fork fixes this? Turns out it does!
• The nme sample fails to compile on C++ and HTML5. The latter seems easy to fix, but the former will require changes to PolymodScriptClassMacro.
• Some changes were done to some of the backends to fix compile errors, but some of them were not properly implemented, which means although the code will compile, it will not actually be functional.
• Maybe install all the libraries needed by all of the samples in one go, globally, instead of having each sample install the same libraries locally for their respective folders, saving some bandwidth.