https://www.w3schools.com/cssref/css_units.asp
https://gist.github.com/basham/2175a16ab7c60ce8e001
https://getflywheel.com/layout/choose-css-unit-create-better-site-layouts-how-to/
Buenas prácticas:
https://sbsharma.com/best-practice-css-units/
https://medium.com/swlh/css-units-which-ones-to-use-and-avoid-31e4ed461f9
