Customizable 404 page for Vitro/VIVO

[hauschke]

Is your feature request related to a problem? Please describe.
VIVO lacks a helpful and customizable 404 page. It could be a standard VIVO page, but the content should give directions on how to find relevant content in the VIVO, maybe linking to browsing pages, including a search slot etc.

Describe the solution you'd like
A standardized template is created. Bonus points, if it can be customized via SiteAdmin -> page management.

Describe alternatives you've considered
Alternatives would be server side, as far as I know. It would be much better to have something included in VIVO.

Additional context

• https://www.mockplus.com/blog/post/404-error-page-design (horrible website, but there are dozens of guides on how to create a helpful 404 page.