Pass custom parameters to `qs`

This is really the same as #98 but that issue has been locked. The original rational for not adding the ability to pass configuration parameters to `qs` was that package was abandoned. That is no longer the case and `qs` is now actively maintained. As such, I wonder if we might be able to revisit the original request and decision as that ability would be really useful.

Also released is #203 requesting support for custom parsers. That issue is perhaps less important since `qs` is maintained again?

The reason I'd like to see this, is that if I submit something like `l-2[].dp-1` then the parameter in `req.body` is _always_ `l-2` regardless of what follows the `[].` (I think the same applies with just a `.`) due to the lack of support being able to set `allowDots` in `qs`.