React-jsonschema-form: allow custom widget for oneOf / anyOf select

[a-b-r-o-w-n]

Prerequisites

• [x] I have read the documentation;
• [ ] In the case of a bug report, I understand that providing a SSCCE example is tremendously useful to the maintainers.
• [ ] Ideally, I'm providing a sample JSFiddle or a shared playground link demonstrating the issue.

Description

When providing a custom select widget, I expected it to be used for the oneOf / anyOf select. The MultiSchemaField component just renders a select instead of looking up the select widget (link).

Steps to Reproduce

1. Create a schema with a oneOf / anyOf property
2. Create a custom select widget and pass to the form: <Form widgets={{ SelectWidget: MyCustomSelect }} />
3. Observe that the select used for the oneOf / anyOf does not render the custom widget.

Expected behavior

I would expect that my custom widget would be rendered instead.

Actual behavior

A select element is used.

Version

1.3.0

[a-b-r-o-w-n]

@epicfaace I'd be happy to take a stab at this.