Fix error on server side

[shrpne]

I have an issue with this polyfill using it with SSR. I have added a simple check, so now it does nothing when running in the Node.js environment.

[kumarharsh]

In the meanwhile, you can use this fork which has @andrejpavlovic and @shrpne's changes https://www.npmjs.com/package/@playlyfe/custom-event-polyfill

[evocateur]

This fix is not sufficient to guard an actual node.js server environment, you need to use typeof window === ‘undefined’ instead of !window

[shrpne]

Thanks! I've updated this check

[kumarharsh]

Has been merged in my fork. New version released.