Add stricter check for CSS selectors styling elements

seed/challenges/html5-and-css.json

@@ -377,6 +377,7 @@
         "assert(!$(\"h2\").attr(\"style\"), 'Remove the style attribute from your <code>h2</code> element.')",
         "assert($(\"style\") && $(\"style\").length > 1, 'Create a <code>style</code> element.')",
         "assert($(\"h2\").css(\"color\") === \"rgb(0, 0, 255)\", 'Your <code>h2</code> element should be blue.')",
+        "assert(editor.match(/h2\\s*\\{\\s*color:\\s*blue;\\s*\\}/g), 'Ensure that your stylesheet <code>h2</code> declaration is valid with a semicolon and closing brace')",
         "assert(editor.match(/<\\/style>/g) && editor.match(/<\\/style>/g).length === (editor.match(/<style((\\s)*((type|media|scoped|title|disabled)=\"[^\"]*\")?(\\s)*)*>/g) || []).length, 'Make sure all your <code>style</code> elements are valid and have a closing tag.')"
       ],
       "challengeSeed": [