FR: quantile regression

### Summary

To regress quantiles, not just a single value. 

Ref https://arxiv.org/abs/2202.05265



### Rationale

Quantiles provides bounds

### Implementation

Lift and shift from https://github.com/lightning-uq-box/lightning-uq-box

CC @nilsleh 

### Alternatives

_No response_

### Additional information

_No response_