feat: search score in search results

[dopry]

It would be nice to be able to query the annotated search score on queries like { pages(searchQuery: "keyword") { ... } }

When searchQuery isn't provided it would return None
When the search backend doesn't support scoring (looking at you sqlite) it would return None.

I did a test by adding qs.annotate_score("search_score") in grapple.utils.resolve_queryset an grapple.utils.resolve_paginated_queryset and updating page interface with postgres and it's working... but the changes to implement testing with postgres run deep.