Tutorial container and instruction

[vsoch]

We got good feedback today that it would be nice to have our Flux Tutorial more easily available on demand, and I agree. For this, after we finish for RADIUSS I'll build a final variant of the "spawn" image and add some page here that more officially shows how to run it.

### Tasks
- [ ] Build final spawn container based on RADIUSS 2024 tutorial
- [ ] Add documentation page here with instructions to use it