Universe: explicitly indicate empty result list

[rwmpelstilzchen]

Scenario

1. Navigate to https://typst.app/universe.
2. Type in the search box some string that yields no results, say foobar.
3. Hit ↵ Return.
4. You are greeted with https://typst.app/universe/search/?q=foobar, which has (apart from the side bar etc.) only a search box populated with the previous search (foobar) and a blank page.

The problem

Now the user doesn’t know whether the page is blank because it’s loading, because there are no results, or maybe because something is broken 🤷‍♀️

A proposed solution

Instead of a blank page show some indication the search yielded no results (‘No results matched your search.’ or something like that). This makes using Typst Universe less confusing and more clear and welcoming 🙂