Extend support of IntersectionObserver for Opera Mini

[matzimowski]

fixes #173

[JakeChampion]

Hi @matzimowski, have you tested whether the polyfill does infact work in those browsers?

[matzimowski]

Hi @JakeChampion
I have used some emulator to check it (usage is described here: https://dev.opera.com/articles/installing-opera-mini-on-your-computer/)

you can see the user agent below:

I've used IntersectionObserver in some SSR project and page was not working well:

but when I changed from features=IntersectionObserver,... to features=IntersectionObserver|always,... it started working properly:

Unfortunately, I didn't manage to find a device to verify it manually.

[JakeChampion]

Emulators are perfectly good to use for testing this type of work, I use all the emulators on BrowserStack for testing :-)

Thanks for showing me that it does work, I feel confident accepting this change now 👍

[matzimowski]

@JakeChampion thank you!