feat: Added dynamic query function

[ardsh]

This change is backwards compatible, it adds the option to specify a function in the query. The main use case here is to allow more complex filters to be used on inner fields that aren't exposed, but other use cases are also possible, e.g. it makes combining with other query builders and slonik helper utilities easier.

[gajus]

@ardsh FYI, this has been ported to Slonik monorepo.

If you are comfortable with it, I will port your patch to https://github.com/gajus/slonik/tree/main/packages/slonik-dataloaders