Add docs about parsing nested qs objects

Fixes #44

DOCS.md

@@ -70,7 +70,11 @@ To run a querier, start by creating a new instance of one:
 const querier = new UserQuerier(query, builder, (config = {}))
 ```
 
-- `query` is a parsed query string, like Express' `req.query`.
+- `query` is a parsed query string, like Express' `req.query`. (Make sure your
+  framework uses a query string parser that supports nested objects. Node.js's
+  native [`querystring`](https://nodejs.org/api/querystring.html) module _does
+  not_, but a package like [qs](https://github.com/ljharb/qs) does. It's usually
+  a simple config change to switch.)
 - `builder` is a query builder / ORM object that the configured adapter works
   with, like Knex.
 - `config` is an optional instance-specific config that overrides the global

README.md

@@ -33,6 +33,12 @@ QueryQL takes a parsed query string (like Express' `req.query`) and translates
 it into the appropriate function calls that your query builder / ORM understands
 to filter, sort, and paginate the records.
 
+(Make sure your framework uses a query string parser that supports nested
+objects. Node.js's native
+[`querystring`](https://nodejs.org/api/querystring.html) module _does not_, but
+a package like [qs](https://github.com/ljharb/qs) does. It's usually a simple
+config change to switch.)
+
 Let's consider an example to illustrate:
 
 ```