text: Title: Add `.quantile(foo=quantiles)` API?
  Body: ### Is your feature request related to a problem?
  
  Many of our methods allow the equivalent of `.shift(foo=5)`, where `foo` is a dimension name.
  
  But not `.quantile`! That requires `.quantile(dim="foo", [0,0.5,1])`
  
  ### Describe the solution you'd like
  
  I guess this is a missing thing rather than a deliberate choice, is that right?
  
  ### Describe alternatives you've considered
  
  _No response_
  
  ### Additional context
  
  _No response_