Write a function, .vreplace() that extends the String prototype by replacing all vowels in a string with a specified vowel.
"apples and bananas".vreplace("u") ➞ "upplus und bununus"
"cheese casserole".vreplace("o") ➞ "chooso cossorolo"
"stuffed jalapeno poppers".vreplace("e") ➞ "steffed jelepene peppers"