Migration to TS & overall refactoring

[aiman-al-masoud]

So I just started working on the add-typescript/ branch. I will simultaneously make some major changes to the overall architecture of the program, to better handle state-management.

The aim is to remove the various singletons & static stuff (Language, Settings, UserProgress, etc...), replacing them with a single Context facade to be passed down to all children from the app's root, as a centralized "source of truth" for the state throughout the app.

It may take me a while to migrate all of the codebase to TS, but I will probably merge to main as soon as I get most of the architecture stuff sorted out, even if there be still some marginal parts in JS.

Another thing I'd like to do is adding some automated tests, eventually, but probably not very soon.

Thanks!

[aiman-al-masoud]

Mostly done! still some issues at hand, detailed in TODOs.