Sam Gubernick

Made changes for C++, general usability

1

-Moved dynamic easing functions to dedicated file -Added regular functions and namespaces -Removed dependency from easing.cpp (now in easing_dynamic.cpp) -Added decimals to whole numbers (1, 2, ... are now 1.0,...

I believe this matches basically the SDL2 backend but it works for SDL3. I added an overload for init() since I want to specify which device it uses.