document allowsInlineMediaPlayback, an important step to make it work inside iOS WebView

[benma]

qr-scanner puts a playsInline attribute on the <video> element. In iOS WebView, this has no effect unless you explicitly enable it:

let config = WKWebViewConfiguration()
// The QR code scanner uses a <video> element with an playsInline attribute.
// This setting allows this attribute. Otherwise the QR code scanner would
// go full screen and contain player controls (pause button),
// a "livestream" label and casting abilities.
config.allowsInlineMediaPlayback = true;        

let webView = WKWebView(frame: .zero, configuration: config)

// ...

It took me some time to figure out why the scanner was completely borked on iOS, so I think it would be helpful to put this info in the README.