fix(curriculum): missing `:root` test to skyline css challenge (#46427)

* fix/added missing test to skyline css challenge

* fix(curriculum): missing :root

curriculum/challenges/english/14-responsive-web-design-22/learn-css-variables-by-building-a-city-skyline/5d822fd413a79914d39e993d.md

@@ -14,6 +14,7 @@ Add a `:root` selector to the top of your media query. Then redefine all four of
 You should add a `:root` selector to the media query.
 
 ```js
+assert.notDeepEqual(new __helpers.CSSHelp(document).getRuleListsWithinMedia("(max-width: 1000px)")?.find(x=>x.selectorText === ":root"), undefined);
 ```
 
 You should add `--building-color1` with a value of `#000`.