Support for IPTC tag Digital source type

### Is your feature request related to a problem? Please describe

_No response_

### Describe the solution you'd like

It would be nice if we could extend

https://github.com/dlemstra/Magick.NET/blob/48c187cf695f44001a832268b221a2fee85d48c1/src/Magick.NET.Core/Profiles/Iptc/IptcProfile.cs

With support for

https://cv.iptc.org/newscodes/digitalsourcetype/

This tag is used to indicate from where the digital asset was created and widely used within generative AI to indicate that it is an AI generated image.

### Describe alternatives you've considered

Perhaps we can somehow workaround this manually?

### Additional context

_No response_

Start in src/Magick.NET.Core/Profiles/Iptc/IptcProfile.cs and compare its existing IPTC tag definitions with the IPTC Digital Source Type specification at cv.iptc.org/newscodes/digitalsourcetype/. Add support for the specified tag so AI-generated and other digital source values can be handled consistently, then verify the profile behavior using the repository's relevant tests.

Written by the indexing model from the issue text.