Need support for styled-component interpolated values (e.g. `css`)

[jdconner]

Expected code:

import styled, { css } from 'styled-components';
import createTheme from 'styled-variants';
import { keyframes } from 'styled-components';

const spin = keyframes`
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
`;

const LoaderTheme = createTheme('Loader', {
    borderRadius: '50%',
    width: '2em',
    height: '2em',
    animation: css`${spin} 0.6s linear infinite`,
});

Error when trying to use the code above:

Related: https://www.styled-components.com/docs/api#css