Email validation form w/ grid, basic custom properties & JS-validation

This exercise has gone a long time. I started it in may this year and somehow forgot about it. Finished it this week, rewrote some of the CSS I'd written then and spend time looking on how to do form validation. This is my first successfull attemt at implementing form validation, so I'm happy for that.

Feedback on the code is very much appreciated. I think I added all a11 for this project. My JS could probably more concise.