How to use interceptors

I am seeing hints of interceptors, but I don't think they're published or used at all for that matter.

https://github.com/posva/mande/blob/9986ba5e7b01ba6bc492f31bf59fdfd19866fc1a/src/interceptors.ts#L7

I would like to `stringifyQuery()` differently, basically all the query values that are arrays, are being sent as CSV but I would like to change that.

Thank you.
