Implement FSR 2.1 (Video attached showing potential performance improvements)

[alexhowell610]

Normally FSR wouldn't really benefit Minecraft because it's a very CPU intensive game but with shaders the GPU is utilized enough to warrant the addition of FSR.

Here's an old video of someone using a fairly hacky way to use an early version of FSR on Minecraft with shaders. As you can see the benefits are pretty exceptional. The improvements with FSR 2.1 and a real implementation could achieve massive performance gains.