This commit introduces an option to control the way components are pushed into the stack.
When pushing components into a stack, they are pushed the moment they are measured.
If `waitForRender` is true, components will be pushed only after the initial render.

api:

```js
options: {
  animations: {
    push: {
      waitForRender: true
    },
    showModal: {
      waitForRender: true
    }
  }
}
```