fix(ui-canvas): iOS bitmaps are flipped during initialization

[CatchABus]

It seems that iOS blank bitmaps need flipping during initialization.

[CatchABus]

@farfromrefug Does _createContextFromImage really need the save/restore part? As a user, I imagine myself drawing few things on top of given image or even scale it. See https://github.com/nativescript-community/ui-canvas/blob/master/src/ui-canvas/canvas.ios.ts#L1852

[farfromrefug]

@CatchABus i see what you mean yes we can remove save / restore part so that you can draw on the image with the correct scale.

[CatchABus]

@CatchABus i see what you mean yes we can remove save / restore part so that you can draw on the image with the correct scale.

Done! Thanks for confirmation 😃