Unnecessary `defer`

[brettz9]

dynamic-import-polyfill/importModule.js

Line 19 in dda7fd2

script.defer = "defer";

Per https://jakearchibald.com/2017/es-modules-in-browsers/#defer-by-default :

Module scripts behave like defer by default – there's no way to make a
module script block the HTML parser while it fetches.

Module scripts use the same execution queue as regular scripts using defer.

...so I think the above line can be removed.

Thanks for the cool polyfill, by the way!