Is your feature request related to a problem? Please describe.
I use some low end computers to play the game. The problem is that some of them can't handle thegame in a medium sized window.

Describe the solution you'd like
Add an option to render at a 60% or 40% of the resolution, like optifine.

Describe alternatives you've considered
Allow to set the render resolution to some steps like 0.5, 0.7 and even 1.5 or 2 for high end systems
Additional context

screenshot of the feature in optifine

Closing as a duplicate of #121