migrate select, number, and text widgets

packages/netlify-cms-widget-select/src/SelectPreview.js

@@ -0,0 +1,13 @@
+import PropTypes from 'prop-types';
+import React from 'react';
+import { WidgetPreviewContainer } from 'netlify-cms-ui-default';
+
+const SelectPreview = ({ value }) => (
+  <WidgetPreviewContainer>{value ? value.toString() : null}</WidgetPreviewContainer>
+)
+
+SelectPreview.propTypes = {
+  value: PropTypes.string,
+};
+
+export default SelectPreview;