insertAfter method
Inserts a new value after a given index
Implementation
void insertAfter(int index, T newVal) {
index = min(value.length - 1, index);
index = max(-1, index);
index += 1;
final change = GgChange(
oldValue: value,
newValue: [...value]..insert(index, newVal),
type: GgChangeType.insert,
index: index,
);
_syncAndApplyChange(change);
}