Make ScrollContainer's .focus() operational

### What is the problem or limitation you are having?

Currently, ScrollContainer cannot accept focus. This means we don't have the ability to press `Space` / `Shift + Space` to scroll the page down/up like we do in the WebView, for example.

### Describe the solution you'd like

Make ScrollContainer's `.focus()` operational, so we can set focus to it, enabling the user to press `Space` / `Shift + Space` to scroll down/up the page.

### Describe alternatives you've considered

Make ScrollContainer respond to `Space` / `Shift + Space` by default, without the need to set focus.

The issue with this approach is: We'll have no control. Especially if we have multiple ScrollContainers in view at the same time.

### Additional context

_No response_

Start by locating ScrollContainer and its .focus() behavior, then compare how the WebView handles Space and Shift + Space scrolling. Confirm how focus is assigned when multiple ScrollContainers are visible. Done means a focused ScrollContainer accepts Space and Shift + Space to scroll down and up without changing behavior for other containers.

Written by the indexing model from the issue text.