feat: add accessibility and keyboard navigation to the MultiSelect component

[TahimiLeonBravo]

Specs

• [x] it should get focus on the plus button when the component gets the focus through the tab key
• [ ] if the plus button has the focus it should move the focus inside the component using the arrows key
• [ ] if any element on the component has the focus and the user press the tab key the focus should be pass to the next focusable element on the page