How to fix the height if you add an element to the array?

Question

Vue.js

I add an element to the array by the button, the wrapper has a height of 100px, it simply ignores it. I tried to set it through data, the same thing, I think that the height starts from the last element.
I tried to give ul the maximum height, so he gave the button after the elements, i.e. it is no more than 100px and , and the elements are added further, I will be glad to help or kick to the source!
https://codepen.io/AntonBrock/pen/oOBovY?editors=0110

Answer 1

https://codepen.io/yarkovaleksei/pen/dLNZmZ
Close the div tags and overflow: auto