Diffing issues

Array rendering re-paint if append elements to head

Render function:

```html

• {{ todo }}

Unshift on array state will cause repaint entire the `

` div:

```javascript
function addTodo() {
state.todos.unshift(state.text)
state.text = ''
}
```

The same will happen for `state.todo[1] = 'Text'` and any other operations on array state.

How to solve: Use key for each item, improve the diff for arrays