gl: Learn OpenGL / GLFW

[silbinarywolf]

Why?
Related to #91, I'm currently using the Ebiten framework which is using GL/GLFW. I don't actually really understand how the underlying code works that much, so... I figure the best way to learn will be to dive in and learn how GL/GLFW work.

I figure even if I don't end up rewriting the GML engine to just use GL/GLFW directly, I'll have a deeper understanding of how graphics rendering works and possibly be able to nail down the cause in #91.

Alternatively, simply removing the dependency on Ebiten completely will fix this problem as it will ultimately reduce complexity.