Edit exif support raw file

[Aliang-code]

Is your feature request related to a problem? Please describe.
I've been using memories for a few months and everything works great. The only problem is that it doesn't support editing the exif of raw files, so I can't use my free time to annotate my photos on phone so that I can later view the tags in lightroom.

Describe the solution you'd like
Support edit exif for raw files, In particular, the exif needs to be stored in the file so that other applications can parse it, and when jpg and raw are stacked into one photo, should the same exif be saved for both files, or should the raw file be given priority?

Describe alternatives you've considered
I have looked for almost all webdav photo management tools, but none of them can support exif editing on the mobile terminal.

Additional context
This issue is also quite useful, I look forward to it very much：#691

[st8r]

Get this error too with a raw image when trying to edit meta from Memories. The image itself shows, just the 'Edit Metadata' create this error:

Cannot edit IMG_7652.DNG of type image/x-dcraw