Add a Piwigo Share Extension to streamline uploading images to Piwigo from native Photos app

[pokmis]

Is your feature request related to a problem? Please describe.
I frequently "mark up" / "touch up" photos in the native iOS app and struggle to locate them quickly when adding them to a Piwigo album.

Describe the solution you'd like
It'd be great to have a "Piwigo" share extension that's directly accessible from a selected photo (or set of photos) that allows quick upload to a Piwigo album.

Current Flow

• Open Piwigo
• Select an Album
• Click "Add"
• Navigate / Select photo(s)
• Click "Upload"
• Review / Click "Upload"

Suggested Alternative Flow (Using share extension)

• Open Native iOS Photos App
• Select a photo / set of photos
• Click Share and select Piwigo
• Piwigo prompts user to select album
• Review / Click "Upload"

(I started prototyping the idea, it could look something like this...)

[EddyLB]

Yes, we clearly need a Piwigo Share Extension. This will come after the recoding of the upload management.
Duplicate of #284.

[EddyLB]

To be implemented when albums will be stored in a persistent database.