fix(curriculum): css and html test issues (#42045)

* fix: css and html issues

* fix: issues with css test

* fix: allow spaces in solution css

* fix: css tests for use-rgb-to-mix-colors

curriculum/challenges/english/01-responsive-web-design/basic-css/size-your-images.md

@@ -31,8 +31,8 @@ Your `img` element should have the class `smaller-image`.
 
 ```js
 assert(
-  $("img[src='https://bit.ly/fcc-relaxing-cat']").attr('class') ===
-    'smaller-image'
+  $("img[src='https://bit.ly/fcc-relaxing-cat']").attr('class')
+    .trim().split(/\s+/g).includes('smaller-image')
 );
 ```