detect and style focused state for multiselect selected values

[austensen]

In our Multiselect component using react-select, we define a custom version of the MultiValue component for the selected values, but we can't know when it's "focused" via arrow key navigation. It doesn't use ::focus, and the classes don't change, and we don't have the isFocused state for each value like in other situations. The screen-reader still works though, and users can close them with the cursor of the delete key, but we aren't able to style them differently when focused (like highlighting the close button, etc.).

This issue is documented here, and hopefully there'll be a solution soon and we can revisit the issue.

JedWatson/react-select#4017