Bug in PNG compressed iTXt chunk

[reinfallt]

There seems to be a bug in the decoding of compressed iTXt chunks in PNG files. Instead of trying to decompress the actual compressed data stored after the keyword and flags, the data from the start of the whole chunk is sent instead which causes a failure:

metadata-extractor-dotnet/MetadataExtractor/Formats/Png/PngMetadataReader.cs

Line 267 in ed79cc0

if (!TryDeflate(bytes, bytesLeft, out textBytes, out string? errorMessage))

I have fixed the issue in a branch here and will create a PR:
https://github.com/reinfallt/metadata-extractor-dotnet/tree/png_iTXt_compressed

Here is an example png file: