Add no-multi-str to overrides config

[cdfa]

Due to mdx-js/mdx#195, we can't use multi-line template strings in MDX (for use with styled-components for example). Therefore, I think we should disable no-multi-str in the overrides config.

[JounQin]

@cdfa But it does work without empty line:

export default () => `<div>
content
</div>`

I tested it on https://mdxjs.com/playground/

[cdfa]

Hmm, my apologies, it seems to be an issue with another package and not mdx in general.