[Feature]: Add back button to the "Archived Page Not Found" page

[Shrinks99]

Context

Currently users can try opening the requested URL in a new tab, but this doesn't meet the needs of users who are using ReplayWeb.page without the full UI where a back button might be the best use case.

What change would you like to see?

Add a back button in addition to the "open in new tab" option for easy navigation back to the previous page in every view.

[tw4l]

Change in wabac.js

[ikreymer]

Can just add a 'Back' link on the 404 page as a start.