Encoding URL query parameters with a function #948

The functions in expr implement toJSON, and I find myself wanting a toQuery to produce url.Values ¹ (encoded to query string).

My mind is bendy but I think that the expression to compute this with pipes/existing functions is too much for me.

I can create a custom function, is there some need/want for this in expr/, accepting PRs? Is toQuery naming fine if yes, any other expectations to meet for contributions (CLA?)...