backendfrompath should work with S3Path

[felixcremer]

It would be good if the backendfrompath function would work with specific path types.
It might be only to loose the type restriction for the defined method.

ERROR: MethodError: no method matching backendfrompath(::S3Path{Nothing})                                                                                                                                                                                     
The function `backendfrompath` exists, but no method is defined for this combination of argument types.                        
                                                                                                                               
Closest candidates are:                                                                                                        
  backendfrompath(::String; driver)                                                                                            
   @ YAXArrayBase ~/.julia/packages/YAXArrayBase/lAdRh/src/datasets/datasetinterface.jl:84