Show feedback while GitHub API fetches result counts/errors

[nixta]

If you search on a slow connection (or visit a page like this on a slow connection), there is a period of time where no result count shows for the search criteria. This is confusing.

Let's show a spinner in place of the count while it's searching (perhaps on a 100ms delay, to avoid constant flickering as you type on a fast network).

Likewise, if there's an error, perhaps we can show some symbol with a tooltip indicating that there was an error scanning our repos to return a count.