Add keyboard navigation to search

[atomtay]

Describe the feature. What should a user be able to do?
After typing in a search string in the home search bar, the user should be able to use the keyboard (either through tab or arrow keys) to access a search result.

Why do we need this feature?
I always forget that you can't use the arrow keys to select an option, which is a minor annoyance. More notably, though, without any method of keyboard navigation, our search feature is inaccessible to users who do not use a mouse.

Additional context
This feature could be implemented alongside #371 or #372 in a re-implementation of DataCommon search.