Fix count_vowels function to handle uppercase letters by converting input to lowercase

Author: SteliosGee

public/data/python.json

@@ -35,7 +35,7 @@
         "code": [
           "def count_vowels(s):",
           "    vowels = 'aeiouAEIOU'",
-          "    return len([char for char in s if char in vowels])",
+          "    return len([char for char in s.lower() if char in vowels])",
           "",
           "# Usage:",
           "print(count_vowels('hello'))  # Output: 2"