Qubes OS Update: allow keyboard navigation

[emanruse]

The problem you're addressing (if any)

It is not possible to move from element to element (qube lines) in Qubes OS Update, thus possibly checking the details of each updated qube easier (instead of clicking and clicking).

The solution you'd like

Allow keyboard navigation.

The value to a user, and who that user might be

Improved UX, less mouse clicks.

Completion criteria checklist

(This section is for developer use only. Please do not modify it.)

[andrewdavidwong]

Related: #7635