Possibly leverage code from other open source project to read .pdn files

[lammel-hub]

Description
Pinta is on its way to become a great replacement for Paint.NET for Windows users (and thereby enabling them to leave Windows).

However, there is a hurdle for taking the leap: Last I tried, Pinta could not import pi.pdn files created by Paint. NET.
This makes migration hard for users with many previously created files in Paint.NET.

Request
Would it be possible to look into this as part of the roadmap for Pinta?

Additional context

• This is one I found that could be useful: https://github.com/drAshcroft/SciImage (have not tested, as I am not a programmer)

• Another Open Source Application called LazPaint (written in Lazarus Pascal) has implemented an import/open .pdn file function that works flawlessly. Their libraries are found at https://github.com/bgrabitmap/
  ("Why not use LazPaint instead, if it is so great" you might ask. It has not been updated since 2022-08...)

• I have also found this: https://github.com/addisonElliott/pypdn (have not tested, as I am not a programmer myself... and also not updated in a while)

[cameronwhite]

See also #827 for a related discussion - there was a community addin for Pinta 1.x which could load pdn files, so this might be possible to resurrect for Pinta 2.2

[lammel-hub]

@cameronwhite that's a great point! The addins are sorely missed in Pinta 2.