Lack of disabled attribute on select element causing color contrast issue

[mellis481]

When isDisabled is set to true, the disabled attribute is correctly added to the <input> element that makes up react select.

https://codesandbox.io/s/codesandboxer-example-forked-dsc99j

Unfortunately, the actual select element (or rather the div that represents the select) is not properly identified as disabled and, as a result, tools like Accessibility Insights for Web complain that color contrast requirements are not met. Color contrast requirements do not need to be met for disabled controls, but tools are not seeing the select as disabled because it is not marked up properly.

This can be solved by added aria-disabled="true" to the control--is--disabled node.