Ignore config in top level directory only

Change .gitignore to only ignore the config files in the top level
directory of repository.  If these files exist elsewhere it's likely
either intended or an error.

.gitignore

@@ -32,10 +32,9 @@ Factorio*
 /instances
 /sharedMods
 /database
-database/items.db
-config.json
-config-control.json
-config-slave.json
+/config.json
+/config-control.json
+/config-slave.json
 package-lock.json
 secret-api-token.txt
 mod_cache.json