Change default search to boolean AND

[p-galligan]

Is your feature request related to a problem? Please describe.
Search currently defaults to the boolean OR operator. Initial testing suggests that this was unexpected by users.

Describe the solution you'd like
Change default search to boolean AND and do more testing.

Additional context
This page outlines some general process to make the change: https://aaronluna.dev/blog/add-search-to-static-site-lunrjs-hugo-vanillajs/

I think this would also cover exact phrase matching, since that is what the search would default to.