Make use of pmap configurable

[baggepinnen]

Hello and thank you for this neat package!

I was wondering if it would be possible to configure the use of pmap, or rather, to avoid it? The reason is that Pluto notebooks are incompatible with the Distributed standard library, so it is impossible to use this package from within Pluto since the use of pmap is hard coded.

I sometimes make use of the pattern

function my_function(input; map = pmap)
   ...
   map(f, x)
end

and that way, the user can pass in another mapping function, for example my_function(input; map = map). Maybe the mapping function could be added as an option?