Mention react-native-squircle-view in the readme?

[aleclarson]

https://github.com/everdrone/react-native-squircle-view

PS: I ported this library, react-native-super-ellipse-mask, to work on macOS via my fork of react-native-macos. You can see the changes I made here if interested.

I even added borderWidth/borderColor support in this commit, which was especially tricky since I wanted it to be (almost) identical to borders in react-native core. For example, the border must appear under any children and never exist beyond the bounds of the view.

I didn't know about react-native-squircle-view until today, after I finished porting.. 😅