input: Write a function to identify and return the first vowel found in a given string. If no vowel is found, return an empty string. The function should consider both uppercase and lowercase vowels. The function should be named vowelCheck.
  assert vowelCheck("Hello World")=='e'
  assert vowelCheck("Python Programming")=='o'
  assert vowelCheck("Sky")==''
  assert vowelCheck("Aquarium")=='A'
  assert vowelCheck("")==''
output: def vowelCheck(s):
      vowels = "aeiouAEIOU"
      for char in s:
          if char in vowels:
              return char
      return ""