Breakpoints - max-width - add Comparison Operators explanation

[asidelnik]

Idea - add Comparison Operators explanation to breakpoints docs:
max-width(selected length) is similar to if(screen length <= selected length)

• Can be added to the "Beginner's guide to media queries".
• Could be useful for JS developers

[bsmth]

Thanks for reporting. There's something on that doc now about ranged values in this format:

@media (30em <= width <= 50em) {
  /* … */
}

• https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/CSS_layout/Media_queries#using_ranged_syntax

I'm going to close as resolved, but if you think there's still room for improvement, let me know. We'd also accept a PR for improvements here:

https://github.com/mdn/content/blob/main/files/en-us/learn_web_development/core/css_layout/media_queries/index.md

Thanks!