Doesn't work outside of DOMContentLoaded

[stevenvachon]

import 'date-input-polyfill';

<script src="app.js"></script>

TypeError: null is not an object (evaluating 'document.body.appendChild')

Likely caused by this:
https://github.com/jcgertig/date-input-polyfill/blob/master/date-input-polyfill.js#L21

Will you accept a PR? I see that there're unmerged PRs.