Support Railpack as a deployment strategy

### Description [Railpack][] is the [formal successor](<https://github.com/railwayapp/nixpacks/commit/144b4f9ab1c3943af4dfe76d3c79d91263f5b465>) to Nixpacks. Kubero should support Railpack as an alternative to Nixpacks. [Railpack]: <https://railpack.com/> ### Possible solution Kubero should support Railpack as a deployment strategy. ### Alternatives _No response_ ### Additional information See <https://blog.railway.com/p/introducing-railpack> for the release announcement.