Document the purpose of each file

[NikitaRevenco]

I'm trying to understand how the whole project works, and I find myself having to scroll very far into files to see the kind of functions and capabilities they have, to just figure out what the file actually does.

Quite a lot of the files have thousands of lines within them, this repository in itself is so incredibly large

It would be really useful if each file had like a few lines of comments at the top describing the purpose of the file and the place it has within the project

There is ARCHITECTURE.md, and it does help me out a bit, but it's not really enough.

Like it would be useful to have such comment headers in each file, and then the ARCHITECTURE.md is expanded to explain how the entire editor works at a high level