Schema with dict field in query [OAS3]

Hi,

I've not been able to figure out if there is a supported way to control the [style](https://swagger.io/specification/#parameter-style) for an argument.

Example schema usage
```python
class Example (Schema):
f = fields.Dict()

@blp.route("/")
class Demo (MethodView):
@blp.arguments(Example, location='query')
def get(self, args):
return 'ok'
```

which yields this spec fragment:
```yaml
- name: "f"
in: "query"
schema:
type: "object"
```

But, as objects passed as query args, have a default style of `form` with `explode` true, the `f` part is not included in the request query when using swagger UI.

At the very least, `explode` needs to be set to `false` in order to reveal the `f` argument name in the query. Or, a `style` of `deepObject` should also work. Frankly, I don't really care which way, as long as it is parsed properly by webargs.

```yaml
- name: "attrs"
in: "query"
style: deepObject # this
explode: false # or this
schema:
type: "object"
```

Right now, I get a
```yaml
{
"code": 422,
"errors": {
"query": {
"moo": [
"Unknown field."
]
}
},
"status": "Unprocessable Entity"
}
```

for a request where `f` is provided as `{"moo":"data"}` in swagger ui.

Start at the @blp.arguments(Example, location='query') entry point and trace how the OAS3 query parameter schema is generated and then parsed by webargs. Compare the emitted style and explode settings with the Dict field behavior; done means Swagger UI sends the f argument and the request parses without the shown 422 error.

Written by the indexing model from the issue text.