You probably need the browser-support interface added, as most electron / nwjs apps do.
As an aside, if you’re planning on publishing popcorn-time to the store, expect it to be removed promptly. Last I heard discussions on this app, it wouldn’t be allowed in the store. But that may have changed.
The High Court yesterday ruled that five of the UK’s biggest broadband providers begin blocking five websites offering the streaming software for download. Sky, BT, EE, TalkTalk and Virgin Media will all be forced to comply, just as they have with popular Bittorrent websites like ThePirateBay (even if those blocks have later been rendered useless).