add sentry into settings.defaults

services/spelling/config/settings.defaults.coffee

@@ -12,4 +12,7 @@ module.exports = Settings =
 	cacheDir: Path.resolve "cache"
 
 
-	healthCheckUserId: "53c64d2fd68c8d000010bb5f"
+	healthCheckUserId: "53c64d2fd68c8d000010bb5f"
+
+	sentry:
+		dsn: process.env.SENTRY_DSN