PNG: Support date field used by Windows

[StefanOltmann]

If a date is configured in Windows Explorer or Microsoft Photo, the system does not generate EXIF or XMP metadata for it. Instead, it creates a tEXt chunk with the label Creation Time.

To enhance compatibility with Windows, the library should be capable of both reading and writing this specific field.

Users may anticipate that Ashampoo Photos will showcase the date taken as seen in Windows Explorer. Any disparity might lead them to believe that Photos is malfunctioning, especially considering that even Windows 11 does not accurately display PNG EXIF data.

Using https://stefan-oltmann.de/exif-viewer/ the output for the relevant part of the test.png is this: