Exercise: count the vowels

Write a function function countVowels(text) that returns how many vowels the string text contains. The vowels are a, e, i, o and u.

• countVowels("javascript") → 3
• countVowels("hello world") → 3
• countVowels("rhythm") → 0

Constraints: text consists of lowercase Latin letters and spaces and may be an empty string, for which the answer is 0; the letter y does not count as a vowel.

Do not add extra imports unless the task says so explicitly.