Issue Emotion.js, "illegal escape sequence in your template literal"

Hi,
I'm having trouble when building components that use Emotion's template literal syntax.

```js
export const Component = styled.div`
background-color: 'blue';

&:hover {
background-color: 'red';
}
`
```

I get the error log:

> You have illegal escape sequence in your template literal, most likely inside content's property value.
Because you write your CSS inside a JavaScript string you actually have to do double escaping, so for example "content: '\00d7';" should become "content: '\\00d7';".

[You can read more about this here](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals#ES2018_revision_of_illegal_escape_sequences)

---

Technically, using `@emotion/babel-plugin`, should fix it; [see this thread](https://github.com/emotion-js/emotion/issues/1755)

Nothing seems to work, and I haven't encountered this issue using webpack on other projects.

> My `babel.config.js` does seem to be used by `microbundle`, so I don't know why I have this issue.

Reproduce the build with the Emotion template literal shown in the issue, then inspect babel.config.js and how microbundle applies the Babel configuration. Compare the resulting behavior with the reported webpack behavior. Done means the sample builds without the illegal escape sequence error or the configuration limitation is clearly documented.

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