Use shape detection API to scan QR codes

[derwehr]

related to #229

[derwehr]

from https://developer.chrome.com/docs/capabilities/shape-detection#os-support

Barcode detection is available on macOS, ChromeOS, and Android. Google Play Services are required on Android.

Only the FaceDetection and TextDetection API are available on my machine.

[aharth]

Looks like the browser API relies on operating systems support.

Not to self: ask Tom about the status next time I see him.

Related: https://zxing-js.github.io/library/