Allow ImageCapture API to enable accepting images direct from mobile camera

[cameronelliott]

I suspect this isn't too difficult, but it would be cool if there was a 4th option beyond: file,image,text
"image from camera"

I think the correct API is the ImageCapture API: https://developer.mozilla.org/en-US/docs/Web/API/ImageCapture

[cameronelliott]

This might marginally reduce "secret exposure area/risk" by removing the step where an image is saved to disk outside the browser before being encrypted.

[mprimi]

I like the idea!