[jQuery] Replace CSS toggle class with built-in function

[vegetabill]

We are using jQuery DOM selectors to toggle classes and visibility in main.js but now all of those functionalities are part of the browser built-in functions.

Replace all class toggles, e.g. $('.letter').toggleClass('uppercase'); with the equivalent using the standard document.querySelector and Element.classList

[soxinmypocket]

I would like to work on this one

[y-martinez]

This issue is available?