Stage a percentage rollout deterministically per user.
Write `isInRollout(userId, rolloutPercent)` hashing `userId` to a number 0-99 (sum of char codes mod 100) and returning `true` if that value is less than `rolloutPercent`.
Required in your answer: charCodeAt
Transpiled, then run in a sandbox
function isInRollout(userId, rolloutPercent) {
// TODO
}
