Support for HoloLens 2 Reading Mode

[Zee2]

Describe the problem

Reading Mode as implemented in MRTK v2 is incompatible with URP. This would be a great fit for an MRGT feature, as it is a low level (and possibly "accessibility"-related feature) tied to render features and overall graphical quality of the MR app.

Describe the solution you'd like

Some sort of opt-in URP render feature thingy that enables Reading Mode!

Describe alternatives you've considered

Not using URP :(

Additional context

MRTK issues: microsoft/MixedRealityToolkit-Unity#10337, microsoft/MixedRealityToolkit-Unity#8344, microsoft/MixedRealityToolkit-Unity#8651, microsoft/MixedRealityToolkit-Unity#8808

Reading mode info: https://docs.microsoft.com/en-us/hololens/hololens2-display#what-improvements-are-coming-that-will-improve-hololens-2-image-quality