Add support for HDR/EDR photos and videos#113

On recent iPhones if you take a picture or video of a bright subject (e.g. the sun), this part of the image is displayed much brighter inside the stock photos app. This takes full advantage of the maximum possible brightness of the XDR displays.

In Darkroom, such photos and videos are displayed in the standard SDR range only.
Just take a picture of the sun and look at it in both apps on current iPhones.

Find more information about this here.

Darkroom should also preserve the HDR information when saving or exporting an HDR photo or video to other apps (i.e. save copy or as a new image).
Currently the HDR information seems only preserved when using the Save menu option (Replacing the original asset)