[Feature Request] Export metrics to shared memory

[RouHim]

Description
It would be awesome if Mangohud could write some basic metrics like FPS and Frametimes to shared memory.

Motivation
I am currently writing an application that allows sensor data to be displayed on an external display (similar to AIDA64). Of course I also want to display the current FPS. Currently I parse the values from the mangoHUD log, which is very not very performant and error-prone.