Add keyboard navigation links and scrolling for jumping in import modal

[bjester]

Summary

Adds keyboard navigation links that support jumping between sections of the import modal screens, that are only visible when navigating by keyboard. Also leverages the focus behavior to scroll top into view.

• Adds 'Jump to recommendations' link that appears in keyboard navigation after search box
• Adds 'Jump to search' and 'Jump to search results' that appears at the top of the recommendations box
• Adds 'Jump to top' that appears at the bottom of both search results and the recommendations links
• Scrolls to top when opening a channel for browsing, changing a browsing topic, or switching search pages

Out of scope: the 'Channels' select box causes KDS modality tracking to lose its keyboard state

References

closes #5268
fixes #5332

Reviewer guidance

• Does tabbing after focus in the search box immediately show the link?
• Does either section's jump link work regardless of whether you're on the default channel list, browsing a channel, or performed a search?
• Does using 'Jump to top' work on either section?

[AlexVelezLl]

Code changes looks good to me!

[AlexVelezLl]

Nice, didn't know we can save just the first reference of a list this way

[bjester]

I didn't know it either! Apparently this is a more future proof approach for Vue 3