chore: rename css skyline (#44211)

* chore: rename files

* chore: update codebase

* chore: proper title case

* chore: block name

Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

curriculum/challenges/_meta/learn-css-variables-by-building-a-city-skyline/meta.json

@@ -1,8 +1,8 @@
 {
-  "name": "CSS Variables Skyline",
+  "name": "Learn CSS Variables by Building a City Skyline",
   "isUpcomingChange": true,
   "usesMultifileEditor": true,
-  "dashedName": "css-variables-skyline",
+  "dashedName": "learn-css-variables-by-building-a-city-skyline",
   "order": 8,
   "time": "5 hours",
   "template": "",