Create a function that takes a string and returns dashes on both sides of every vowel (a e i o u).
dashed("Innokodakademija") ➞ "-E-d-a-b-i-t"
dashed("Carpe Diem") ➞ "C-a-rp-e- D-i--e-m"
dashed("Fight for your right to party!") ➞ "F-i-ght f-o-r y-o--u-r r-i-ght t-o- p-a-rty!"