Docs improvement: when to use river vs temporal

[JanRuettinger]

I think it would be helpful to add a section to the docs on when to use River vs other popular services like Temporal.

My use case is the following:

1. User uploads 1-100 documents.
2. All documents need to get processed in three steps. All three steps depend on external services. Each step not take more than 5 seconds.
3. Inform user about progress updates, e.g. how many files were processed already & how many failed

Would it make more sense to use River for such a use case or is Temporal a better choice?