Merge pull request #58 from youngeek-0410/fix/cors

ゲームスタートのレスポンスでCORSを許容してなかったので修正

lambda/room/{room_id}/start/POST/main.go

@@ -176,6 +176,7 @@ func createErrorResponseWithStatus(statusCode int, responseMessage string) (even
 	return events.APIGatewayProxyResponse{
 		Body:       responseMessage,
 		StatusCode: statusCode,
+		Headers:    map[string]string{"Content-Type": "application/json", "Access-Control-Allow-Origin": "*"},
 	}, nil
 }