Proper way of reading MSFT_lod

What is the proper way of reading the MSFT_lod extension with this loader? [See the readme here](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/MSFT_lod)

Strangely, I am able to load the "MSFT_lod" extension part, but I cannot figure out how to access the data for the "MSFT_screencoverage" extras part.

Start with the linked MSFT_lod extension README and the loader's existing handling of that extension. Trace how the MSFT_screencoverage data in extras is represented and determine the access path that should be explained or exposed; done means users can retrieve that data unambiguously.

Written by the indexing model from the issue text.