We need an event/signal to know when the user reaches the last cell

[luongvo]

Following #30, we would like to have an event/signal to know when the user reaches the last cell -> to trigger the OTP validation process automatically. isValid from onValueChange might help, but it could trigger the wrong action when editing a valid input.

For example,

• input is empty, type 1111 -> isValid = true, reached to the last ✅
• input is 1111, edit second char to 2 -> 1211 -> isValid = true, not reached to the last, the user might want to enter more ❌