Add lookup for referees whose names are missing

[pmonks]

Description of Problem:

When the football-data API returns a referee without a name, I want the bot to lookup up the name in a local directory (using the referee's id, as returned by the API), so I can see the referee's name instead of the default ([unnamed referee]).

Potential Solutions:

Add a map of referee-id → referee name to the config.edn, and use that map if and only if the API response is missing a name (i.e. the API always has precedence).

[pmonks]

The maintainer of football-data.org has indicated they've fixed this for some of the more prominent referees, and are looking into fixing some of the other missing names too, so I think this is lower priority now.

I'll leave it open for a bit until we've had a good chance to see the new data in action, and then we can make a call about whether to implement it or not.

[pmonks]

The new data seems pretty good, and the maintainer of football-data.org is responsive to feedback, so I don't think this is necessary.