Update README.md

Author: IlyaLisov

README.md

@@ -44,6 +44,10 @@ To run this application you need to create `.env` file in root directory with ne
 - `MINIO_URL` - URL of MinIO instance
 - `MINIO_ACCESS_KEY` - access key of MinIO
 - `MINIO_SECRET_KEY` - secret key of MinIO
+- `SPRING_MAIL_HOST` - host of mail server
+- `SPRING_MAIL_PORT` - port of mail server
+- `SPRING_MAIL_USERNAME` - username of mail server
+- `SPRING_MAIL_PASSWORD` - password of mail server
 
 ## Guide