Document context: focus on current document

An improvement for opening document context, e.g. view the book that your document is a page of.

This link currently opens at the start of the collection, e.g. the book. If you want to see the page within the book, you have to search for it yourself.

It would make more sense if you immediately opened the page of the current document, and the results focused on that document (by scrolling + focusing on the element).

This would make more sense with #1214 - though the route would probably also need another parameter to set a focused document.

Trace the document-context link and the route that opens the collection, then inspect how the current document is represented in the search results. The work is done when opening context lands on the current document's page and the results visibly scroll to and focus that document, with any needed route parameter handled.

Written by the indexing model from the issue text.