JavaScript best practices

[Cluab]

instead of using the same border multiple times, I can use a class attribute

https://github.com/Cluab/to-do-list/blob/master/src/style.css#L36

add all of the global consts to the start of the page.

https://github.com/Cluab/to-do-list/blob/master/src/index.js#L7:~:text=from%20local%20storage-,const%20retrieveData%20%3D%20localStorage.getItem(%27list%27)%3B,const%20body%20%3D%20document.querySelector(%27body%27)%3B,-body.onload