Add Railway deployment button to README

Added a deployment button for Railway in the README.

Signed-off-by: Marc <[email protected]>

Author: MarcBlattmann

README.md

@@ -92,3 +92,5 @@ Maybe and Sure are both distributed under
 an [AGPLv3 license](https://github.com/we-promise/sure/blob/main/LICENSE).
 - "Maybe" is a trademark of Maybe Finance, Inc.
 - "Sure" is not, and refers to this community fork.
+
+  [![Deploy on Railway](https://railway.com/button.svg)](https://railway.com/deploy/sure?referralCode=bE8vHp&utm_medium=integration&utm_source=template&utm_campaign=generic)