firebase_ml_vision supports FirebaseVisionImage.fromBytes() without FirebaseVisionImageMetadata

[thanhbinh84]

Use case

Given an Uint8List photo, we have to store to a local file in order to convert FirebaseVisionImage

There is a FirebaseVisionImage.fromBytes() function, but it perhaps is for CameraImage only, with the normal photo such retrieving from the Internet, we have to store to a file and then use FirebaseVisionImage.fromFile() that wastes an additional step and space.

Proposal

Update this function

FirebaseVisionImage.fromBytes(
    Uint8List bytes
  )

With FirebaseVisionImageMetadata is optional