update requirement to account for image chooser dependency

[mwesterhof]

This appears to be necessary, I ran into issues when testing react streamfields for an existing wagtail project. Trying to open an image chooser fails with a JS error here

this appears to happen because wagtail-react-streamfield depends on this, which was introduced in wagtail 2.2

[BertrandBordage]

Thank you for pointing that out, @mwesterhof!
I’m trying to fix it in order to make it work with all 2.x versions instead of sticking to 2.2. If I can’t make it, I’ll fallback to your pull request 🙂

[BertrandBordage]

It’s too complex to support both because wagtail-react-streamfield relies on the new onload system introduced in Wagtail 2.2 to asynchronously fetch chooser data and display it.

So I merge your pull request, this project will only support Wagtail 2.2 or more.